Underseat heater fans run with temperature switch, not coolant temperature

[Scott Anderson CLC#26068]

I realize there are many threads regarding the underseat heater connections generally (I'm actually on one of them), but I haven't seen an answer to this specifically;

For context, in my 41 convertible coupe there is now a rebuilt (Jim Tucker) Ranco valve with capillary tube installed to replace the one that was missing when I got the car, control hooked up, jumper from one fan to another installed. The temperature control slide lever now operates the fans regardless of coolant temperature. So, somehow the coolant temp component of the setup is bypassed. (Radiators have been cleaned / boiled out and there is coolant flowing through and between them.)

Does anyone have any ideas on how the connections might be wrong? Further details needed?

Thanks
Scott

[Roger Zimmermann]

If I recall correctly, my cars from the fifties are doing the same: the temperature lever is operating the fan. The fan in those old cars cannot be controlled by the coolant temperature; that came much later when computers (control modules) were installed in cars.

[Jay Friedman]

My '49 (also with a Tucker-rebuilt Ranco valve) operates like your '41 and as Roger says his '50s cars operated.  The temp lever operates the fan too. 

[Bill Ingler #7799]

Scott: You might want to read the attached PDF file on the heater controls on the 46-47 especially the paragraph on Thermostatic Control. The controls might be designed different on the 47 than your 41 but the explanation of thermostatic control should be the same. Slide lever on both, control the temp of the water entering through the Ranco valve to the heater cores as well as the fans. Slide the lever to the full open position when the engine is still cold will bring the fan on but since the coolant coming through the Ranco valve is still cold, the fans are blowing cold air. Waiting until the car temp gauge gets right of the cold mark before moving the control slide lever is recommended.  The fans will operate regardless of the coolant temperature.   Bill

[Bob Schuman]

Scott,
With a properly functioning 1941 Ranco valve, the fans should not operate regardless of the temperature lever position until coolant temperature has warmed after a cold start. My service bulletins do not specify what that temperature is.  That prevents the fans blowing cold air in a cold car.

Later bulletins mention that in 1946 and 1947 cars the temperature lever should be left in the OFF position until the temperature gauge has moved above the COLD mark to avoid the fans blowing cold air.  That appears to indicate that the feature of the 1941 valve had been eliminated. Since the 1941-1947 systems were otherwise the same, it may be that your Ranco valve is for a postwar car without the cold engine lockout feature. I do not have any information for identifying the different valves.
Bob Schuman

[Scott Anderson CLC#26068]

Thank you all for taking a few minutes to reply, much appreciated.

As far as I know, the 1941 valve was a one year only valve; the shop that I had install the valve has my copy of The Serviceman reprints but they report that it says that the fans should not come on until the Ranco senses some heat in the system (as Bob Schuman's comments). I understand from other's comments that that apparantly changed postwar, I'm not disagreeing or arguing.

Jim Tucker did confirm it was a 1941 valve before I bought it in any case. I'm not an electrical guy at all, but I don't see anything in the Ranco diagrams such as Bill provided that show what would drive this. Does anyone else?

Of course I can live with the idea of not blowing air across cold coils, and hoping that when it's warm I do get heat regulation (such as it was in the era anyway). Of course having come this far it would be nice to know I have it right.

[Roger Zimmermann]

Well, I did learn something. This method of not allowing the fan to run until the cooling water was warm was way ahead of the time. This comfort element was rediscovered when cars had ECMs.
I'm wondering why this system was not used on later cars: too expensive or not reliable?

[denniscaddy]

My 41 Fleetwood (ex. Bud Wirthman, won the first Ansel Sackett award) has a totally unmolested deluxe heating system. 

It works amazingly well, controlling water flow (when it is changing the rate of flow you can sometimes hear a slight gurgling sound from the Ranco valve).  It does not start until the water is warm.  The fans' speed changes regularly, and if it is quite cool outside opening a front door will result in a fan increase in just a very short while.  The capacity to heat the car evenly front and rear is excellent.

The only problem it has is that sometimes it won't start unless you reach down and give the Ranco valve just a little tap with your fingertips.  It must be that wherever the electrical switch inside the valve is responding to the water temp, it is sluggish.  Anyway, I certainly am not going to go into it because of this little flaw, unless someone knows a quick, uninvasive fix.   Most of the time it starts and operates flawlessly.

In the cool weather, I leave the temp lever at about  +40% from the left, or off position.

Are there other correctly operating 41 systems out there?

[Bob Schuman]

Dennis,
I know of at least two properly operating 1941 Cadillac Automatic Heating Systems, my own 41-60S that was restored by Bill Podany several years ago, and a 41-6227 coupe that a friend owned from 1971 to 2011. On those cars the fans do not operate until the coolant has warmed somewhat.
I believe the Ranco valve and electrical components on it were ahead of the available technology at the time, and that is why the cold water lockout was eliminated, but that is just my opinion.
Bob Schuman

[Jay Friedman]

My comment on Dennis' observation that he is "certainly...not going to go into [his Ranco valve] because of [a] little flaw, unless someone knows a quick, uninvasive fix", is that based on my experience with my '49's heater unless there is some major problem with it, such as a leak, you leave your heater alone.  If a '41 heater is anything like a '49's, with few exceptions I don't believe there are any uninvasive fixes. 

A year or so ago my heater developed a leak that dripped anti-freeze onto my shoes when driving the car.  Because of its complexity, a search while lying on my back under the dash could not pinpoint where it was coming from.  The only solution was to remove the entire unit.  This first task was to disconnect the levers, wires, vent cables etc., while lying on the floor.  Next, removing the unit could only be accomplished with my wife seated on the floor and pushing from the passenger compartment, while being super careful to not bend the capillary tube (which Jim Tucker and Fab Ornani told me would render it inoperable).  At the same time I was bent over the left fender pulling it into the engine compartment, while being super careful to not damage the gasket between the heater and the firewall (and which is apparently unobtainable from Steele or anyone else).  And that was just the beginning.

On the bench, I never found the source of the leak, but it was probably a bad hose or maybe one of the 2 Ranco valves.  The heater unit proved to be a complex mechanism indeed.  I took lots of photos before dismantling it, but there are a number of sub-units, with lots of fasteners, so that as careful as I tried to be, even with the photos I got a bit dis-organized.  Jim Tucker took a week or so to rebuild the Ranco valves.  In addition, I had to wait a while for new heavy duty Goodyear hoses and Wittek hose clamps to arrive, so by the time I got around to putting it all back to together my aged memory was not totally up to the task. 

The solution was to call Dennis to ask if he'd sell me a complete '49 heater which I would then use as a guide.  Luckily he had one which I purchased.  I finally succeeded in getting everything together and, with my wife again (she deserves a medal), installed back in the firewall.  I was lucky as it now works well, does not leak and I managed to sell at Hershey the left over parts from the unit I bought from Dennis.  Nonetheless, I don't think it's too much of an exaggeration to say it's the most complicated job I've done in the 30+ years I've owned my Cad. 

[Scott Anderson CLC#26068]

The mystery is solved - Cadillac documentation confirms that the fans on the 1941 system should not run until heat is sensed in the system. And by inference that apparantly that was changed postwar. At this point I don't know about the 1942 implementation but I'd hazard a guess that it can be inferred just from the dash controls alone.

Before going into it all it's important to me to be certain to thank each of you for taking some time (sometimes more than once, extra appreciate the sustained interest) to chime in with what they had to add to the mix.

So, This may be a good time to refill your coffee cup or wine glass as the case may be. Remember, I'm not an electrical guy so feel free to continue to add to the information. Emboldened by Bob Schuman and deniscaddy's assertions that the 1941 system should work differently than the postwar cars, I just continued to dig.  Not having either the physical unit handy as the car is in a shop, nor documentation as to how the wiring should work (in a previous post Doug Houston wrote that he had never seen a wiring document for the 1941 system) I went other directions.

The first documentation towards how it was supposed to function comes from the 1941 Cadillac Salesman's Data Book dated 9-13-40. I'll attach the relevant pages there - it leaves no question as to what the intent was. In the introduction to the system it reads "When the car is started, and the water in the cooling system is cold, both fans are completely shut off preventing any blast of cold air on the passengers. After the water in the cooling system is heated both fans are automatically turned on at high speed. They continue at high speed until the temperature reaches the point set on the temperature control, when the fans go to slow speed and water circulation in the heater is restricted." At the end of the section it concludes with "The control lever should be left permanently in the position which provides the most comfortable temperature to the driver, although it can be increased or reduced as desired."

This is in contrast to the postwar (1946-1947) factory documentation which Bill Ingler provided in this thread and Bob Schuman quoted above which instructs that customers should be advised to wait until the coolant has begun to warm (~100F, about a mile of operation, temp indicator just to the right of the Cold mark) before invoking the system. It's the singe best source I've seen generally. (Thanks again Bill and to Bob Schuman who also kindly provided it to us in a previous thread on the same subject.)

So, given that I now knew that something was indeed wrong, I called Jim Tucker since he did verify as I wrote earlier that I did have a 1941 valve. Paraphrasing, it seems that the 1941 system has an internal electromagnetic coil consisting of a thermoplastic/bakelite type material upon which a winding with a thickness of something like .005" acts upon a set of tungsten points, which is how the fans go from stopped to switching on thermostatically. These are susceptible from age / wear, and also can be damaged in the bead blasting process of restoration. He said that there are two wires attached to the valve, one hot & one ground. The hot one is what drives this magnet.

The conclusion is that some piece in that assembly was bad in my unit which, although just now installed, he rebuilt in June of 2015 nearly two years ago. And I'm not blaming Jim - we all know that with old cars things working today may not be tomorrow, "just because". He did have a 1941 unit on the bench this morning, and will be sure to be checking this assembly in his future rebuilds of these units. As for me, rather than accessing the Ranco valve again (like Jay Friedman essentially wrote all I have to do is to remove the car), I'll be treating my prewar setup like a postwar one, not invoking the fans until they're blowing over warm coils. Again I can live with this as long as I know why.

And I've written more here than may seem necessary at the moment, and attached some additional  files of the system pieces thinking of the next folks with a an undertaking on this system doing searches for what information can be had.  Mutual support is at the core (horrible pun, couldn't help it) of what makes our club worth the while.

Thanks everyone again.
Scott

[Bob Schuman]

First please reread the first two sentences of Jay Friedman's second paragraph above. That exactly describes what occurred in my 49 Cadillac over a year ago. My corrective action was much simpler and easier. Years ago I would have undertaken the same fix Jay did, but being older, less able to work under the dash, and maybe a little wiser, I disconnected the three hoses from the engine side of the defroster unit ( I think Cadillac called it the upper heating system), and made a jumper to feed coolant through the underseat heaters without going through the defroster unit.

To those not familiar, the 1949 heating system uses two Ranco valves, one for defroster regulation, the other for underseat heaters regulation, both being within the defroster unit. I would bet that Rube Goldberg was working for Cadillac and designed that system. For you young persons, look him up on the internet.

The underseat heaters now are turned on or off by one of the dash levers as original, with full water flow at all times except when I close my manual valve in one hose for summer use. The defroster fan still works as original from the dash lever, but with no heating effect.

I believe my failure occurred before Jay's did, and his writeup reinforces my belief that my approach was definitely right for me. For anyone doing a total restoration of a 49 Cadillac, my suggestion is that while the dashboard is removed, that would be the time to do anything that may be needed to the defroster unit which is directly behind the instrument cluster. Since my car does not get driven when the weather is uncomfortably cold, the modification is not a problem for me.
Bob Schuman

[Jay Friedman]

I think the key word in Bob Schuman's comments about his approach to dealing with a '49 heater compared to mine is "wiser".  I agree with Bob that if I were, I'd have hooked things up as he did and have water flow going directly to the under-seat heater units at all times with a manual shut-off valve for summer driving.  Unwisely feeling that I wasn't going to let a mere heater defeat me, I spent many more hours than I should have, some very uncomfortable, curing its ills.  Afterwards, I did have a sense of accomplishment, but also was physically drained and for a while afterward didn't feel very much like working on the car. 

And in the end, what for?  I might use the heater 4 or 5 times per year and the defroster even less.  Didn't Cadillac go back to a less complicated heating system in 1950?

[Bob Schuman]

Jay,
Yes, you are correct. In 1950 Cadillac simplified the heater system with only one Ranco valve and no rubber hoses inside the passenger compartment, and only one underseat heater, the one on the passenger side. In my 51, it works as designed and is comfortable on a 25 degree day. Below that, the car stays in the garage. I do not recall such marginal heating from the fresh air heater in my first car, a 1949 Chevrolet, but maybe that is due to a faulty memory or a much younger body not bothered as much by winter weather.

In case anyone thinks I was bragging about the easy "fix" for my 49 defroster leak, if I had that problem ten years ago I would have dove into a major job just like Jay, and suffered for bodily abuse just like Jay.
Bob Schuman

[Scott Anderson CLC#26068]

The mystery is solved - Cadillac documentation confirms that the fans on the 1941 system should not run until heat is sensed in the system. And by inference that apparantly that was changed for the postwar 1946-1947 implementation. At this point I don't know about the 1942 implementation or the 1948. It's clear from comments here and from a friend that is working on one that the 1949 implementation has a different set of circumstances than these.

Before going into it all it's important to me to be certain to thank each of you for taking some time (sometimes more than once, extra appreciate the sustained interest) to chime in with what they had to add to the mix.

So, This may be a good time to refill your coffee cup or wine glass as the case may be. Remember, I'm not an electrical guy so feel free to continue to add to the information. Emboldened by Bob Schuman and deniscaddy's assertions that the 1941 system should work differently than the postwar cars, I just continued to dig.  Not having either the physical unit handy as the car is in a shop, nor documentation as to how the wiring should work (in a previous post Doug Houston wrote that he had never seen a wiring document for the 1941 system) I went other directions.

The first documentation towards how it was supposed to function comes from the 1941 Cadillac Salesman's Data Book dated 9-13-40. I'll attach the relevant pages there - it leaves no question as to what the intent was. In the introduction to the system it reads "When the car is started, and the water in the cooling system is cold, both fans are completely shut off preventing any blast of cold air on the passengers. After the water in the cooling system is heated both fans are automatically turned on at high speed. They continue at high speed until the temperature reaches the point set on the temperature control, when the fans go to slow speed and water circulation in the heater is restricted." At the end of the section it concludes with "The control lever should be left permanently in the position which provides the most comfortable temperature to the driver, although it can be increased or reduced as desired."

This is in contrast to the postwar (1946-1947) factory documentation which Bill Ingler provided in this thread and Bob Schuman quoted above which instructs that customers should be advised to wait until the coolant has begun to warm (~100F, about a mile of operation, temp indicator just to the right of the Cold mark) before invoking the system. It's the singe best source I've seen generally. (Thanks again Bill and to Bob Schuman who also kindly provided it to us in a previous thread on the same subject.)

So, given that I now knew that something was indeed wrong, I called Jim Tucker since he did verify as I wrote earlier that I did have a 1941 valve. Paraphrasing, it seems that the 1941 system has an internal electromagnetic coil consisting of a thermoplastic/bakelite type material upon which a winding with a thickness of something like .005" acts upon a set of tungsten points, which is how the fans go from stopped to switching on thermostatically. These are susceptible from age / wear, and also can be damaged in the bead blasting process of restoration. He said that there are two wires attached to the valve, one hot & one ground. The hot one is what drives this magnet.

The conclusion is that some piece in that assembly was bad in my unit which, although just now installed, he rebuilt in June of 2015 nearly two years ago. And I'm not blaming Jim - we all know that with old cars things working today may not be tomorrow, "just because". He did have a 1941 unit on the bench this morning, and will be sure to be checking this assembly in his future rebuilds of these units. As for me, rather than accessing the Ranco valve again (like Jay Friedman essentially wrote all I have to do is to remove the car), I'll be treating my prewar setup like a postwar one, not invoking the fans until they're blowing over warm coils. Again I can live with this as long as I know why.

And I've written more here than may seem necessary at the moment, and attached some additional  files of the system pieces thinking of the next folks with a an undertaking on this system doing searches for what information can be had.  Mutual support is at the core (horrible pun, couldn't help it) of what makes our club worth the while.

Thanks everyone again.
Scott

[Jay Friedman]

Jay,
Yes, you are correct. In 1950 Cadillac simplified the heater system with only one Ranco valve and no rubber hoses inside the passenger compartment, and only one underseat heater, the one on the passenger side. In my 51, it works as designed and is comfortable on a 25 degree day. Below that, the car stays in the garage. I do not recall such marginal heating from the fresh air heater in my first car, a 1949 Chevrolet, but maybe that is due to a faulty memory or a much younger body not bothered as much by winter weather.

In case anyone thinks I was bragging about the easy "fix" for my 49 defroster leak, if I had that problem ten years ago I would have dove into a major job just like Jay, and suffered for bodily abuse just like Jay.
Bob Schuman

Cadillac must have had lots of complaints in 1949 from their well-heeled customers whose shoes were ruined by a leaking heater hose.  To this day I wonder what Cadillac engineers were thinking when they developed for the '49 Cad what they called the "Automatic Heating and Defrosting System".  That is, what was the problem they were trying to solve?  Like Bob, I've owned cars from that era of various makes with their typical simple heating systems, and they all worked well. 

In fact, in '49 Cadillac did offer something similar as a lower cost option which they called the "Standard Heating System".  In my years of '49 watching I've only seen a couple of cars with this system, one of which was a hearse.  It has no thermostatic controls, only a single under-seat blower and 2 simple toggle switches for heat and defrost under the dash.  Cadillac literature says it was for cars sold in mild climates.  The standard heater was a $55 option in '49 compared to $85 for the automatic system, meaning if you were a cheapskate or lived in the right climate, you could buy a '49 Cad without any heating system at all.

[Brad Ipsen CLC #737]

I'm also in the process of reworking a 49 Heater system but am in a total restoration mode so no dash in place but I am seeing all of the complications of the system.  I am also familiar with the 1940 heater system in its variation which are similar to the standard 49 heater.  If the option price of the standard heater at $55 and the deluxe at $85 reflected the build cost either the standard heater was way over priced at retail or Cadillac was losing a lot of money on the deluxe.  I am still not sure how many rheostats are involved, two Ranco valves, 3 electric motors and fans, 3 radiator cores plus knobs, wires and control cables, etc.

[denniscaddy]

I remember another job on my 49 convertible...replacing the LH wiper transmission.  I did have a nos unit in stock, which delighted me, but the installation was something else again.  I still think it can only be performed by a double-jointed monkey.  That was over 30 years ago, and my old bod wouldn't even allow me to contemplate doing it today.

Jay, glad to hear your heater project worked out OK.

I am now more sure than ever that I am going to leave my 41 system completely alone!

[denniscaddy]

As I recall, getting the braided cables threaded was a real problem.  There is a tensioner which you lock, then unlock and apply tension once you've got it all arranged.  Of course that only takes about 15 tries.  PITA.  But all  part of the joy of old cars.  Anybody can drop their car off at the dealer's and tell them put in the new parts to fix it.  And, OK, only $150/hour.

[bcroe]

I believe the Ranco valve and electrical components on it were ahead of the available technology at the time, and that is why the cold water lockout was eliminated, but that is just my opinion.
Bob Schuman 

For some owners delaying fans until full engine warmup might be desirable.  My
79 E car had such a coolant temp switch, and was driven to work in winter because
of the FWD.  All day that car could sit outside in 20 below zero, and then I would
drive home.  Well I covered MOST of the 9 miles home, FREEZING to death, before
any air came out of the heater.  I decided I would be much happier with air from
50 or 100 degree engine coolant, than sitting in 20 below zero.  I shorted out that
coolant temp switch and started using the heater as soon as I left the parking lot. 
Its still shorted after 3 decades, I still have enough energy to operate the manual
control.  Bruce Roe