Author Topic: '77-'79 blower relay fix  (Read 279 times)

Offline T J Lankes

  • Posts: 43
  • Name: T J Lankes
'77-'79 blower relay fix
« on: June 19, 2017, 02:28:04 PM »
Can anyone post the TSB referenced below or verify that the fix described does indeed correct the blower relay issue on Tri 7s? (assuming that the blower motor  and rest of electrical circuit is good).

Thanks



"coupiedeville
09-27-10, 10:05 AM
I had this blower relay issue for many years on my 1980 Coupe deVille. It was a concern of mine because both the relay and the connector would show the starting signs of melting and I feared sooner or later a dash fire would be the result.

I recently found that GM issued a Technical Service Bulletin (TSB) on this back in 1985. The TSB states the fix is to rewire the old 4 prong relay to a different 5 prong relay (although only 4 of the 5 prongs are used on most of the deVilles). The TSB repair kit part number has changed many times, but the latest part number for the kit is 12167112. It retails for $91.92, but a google search on the part number will give you sources who will sell it for about $60.00. Once I changed this (I made sure to solder all of the connections instead of using solderless connectors provided in the kit), the blower has worked flawlessly ever since."


Offline bcroe

  • Posts: 2059
    • CLC Member
      CLC Member #14630
Re: '77-'79 blower relay fix
« Reply #1 on: June 19, 2017, 08:44:41 PM »
Quote from: T J Lankes

The TSB repair kit part number has changed many times, but the latest part number for the kit is 12167112. It retails for $91.92, but a google search on the part number will give you sources who will sell it for about $60.00. 

That is still an outrageous price for a common relay.  I have a kit for $10 for fuel
pumps, would probably work here if you knew how to wire it.  Bruce Roe

Offline TJ Hopland

  • Posts: 6823
Re: '77-'79 blower relay fix
« Reply #2 on: June 19, 2017, 10:16:33 PM »
In my 78 and several others I had looked at the block the relay was in was melted so unless that kit was the complete new relay block that holds all the relays you might as well save a lot of money and just use a more modern cheap relay.   

On the ones I actually repaired I was able to extract most of the pins from the original block and slide them onto the new relay.   That just left the badly damaged one to repair and replace with a new connector.   I used some heat shrink tubing on the original connectors just in case it banged around there under the dash.  The connectors are the typical female Packard 56's that were commonly used in this era.  They are easy to extract with just a small screwdriver and fit the common universal relays.

For some reason GM has a history of really ripping you off with repair harnesses.   The 95+ trucks had a problem with the blower switch, hmm no history there they could have learned from eh?   I saw there was an updated switch and repair harness so I had the dealer order it and like the Cadillac one it was something like a $90 part but I wanted to do it 'right' so I said go ahead and get me the official GM part.   When it came in it was an empty connector body and one 3" wire and a crimp splice.  Even the parts guy at the dealer said that was a rip and and he would feel bad selling it to me and now knew why they didn't stock em and the shop never ordered one. 
StPaul/Mpls, MN USA

73 Eldo convert w/FiTech EFI
75 Eldo rusty but trusty
80 Eldo Diesel
And other assorted stuff I keep buying for some reason

Offline T J Lankes

  • Posts: 43
  • Name: T J Lankes
Re: '77-'79 blower relay fix
« Reply #3 on: October 26, 2017, 11:09:18 PM »
TJ,

Thanks for the info.  I finally got around to making the repair as you suggested with a Four Seasons relay and now I can run the blower at speeds above LOW with peace of mind.

All the best

Offline TJ Hopland

  • Posts: 6823
Re: '77-'79 blower relay fix
« Reply #4 on: October 27, 2017, 08:33:43 AM »
Just in time if you are up north.  Its suddenly seems like winter where I am and heat would be nice.     
StPaul/Mpls, MN USA

73 Eldo convert w/FiTech EFI
75 Eldo rusty but trusty
80 Eldo Diesel
And other assorted stuff I keep buying for some reason

Online Eric DeVirgilis CLC# 8621

  • Posts: 3937
    • CLC Member
      CLC Member #8621
  • Name: Eric DeVirgilis
Re: '77-'79 blower relay fix
« Reply #5 on: October 27, 2017, 08:50:15 AM »
I once had a blower relay burn out on a 1995 DeVille. Fan had begun running slower then poof- the smoke started coming out of the dash vents. No fire or other damage resulted otherwise.
A Cadillac Motorcar is a Possession for Which There is no Acceptable Substitute

Offline TJ Hopland

  • Posts: 6823
Re: '77-'79 blower relay fix
« Reply #6 on: October 27, 2017, 09:56:11 AM »
The 70's I believe still used a resistor block similar to what the manual controls used.   The controller was just automatically selecting which resistor to use.   80's and up they went to an electronic variable speed module so the control sent a signal to the module that then did the 'heavy lifting'.   I never looked close to see what the actual device was or if they changed over the years. 

Upside to the electronics they were more efficient because instead of just burning off extra power like the resistors did they more or less turn the power on and off quickly to slow the motor down.  The downside to the electronics especially the earlier ones is they could be damaged by noise and spikes in the electrical systems and just like the resistors could be overloaded by bad connections or a dragging motor.     
StPaul/Mpls, MN USA

73 Eldo convert w/FiTech EFI
75 Eldo rusty but trusty
80 Eldo Diesel
And other assorted stuff I keep buying for some reason