ammonman

Relay X has to be energized to send power to the Climate Control head unit via fuse #37. The Climate Control head unit energizes the Blower Relay which sends power to the blower through the blower speed switch. The bad Relay X was causing the Blower relay to intermittently loose power from the Climate Control head unit thus causing the blower to shut off.

Mike

Randy V

Mystery solved - thanks, Mike!

Alan

It also supplies the foglights & daytime riunning lights (if equipped).

Alan

Randy V

A year later -

I continue to have an intermittent fresh air blower.

When it works, the various speed settings work correctly.

As mentioned previously, the power leads at the CE panel had experienced excessive current loading and were crispy. I replaced the wires and installed a new fuse block location.

What else could cause the blower to work intemittently? The associated relay has been check OK (but I have not tried swapping relay X again yet).

Usually when I start the car the blower will not operate, but after 20 minutes or so of driving the blower begins to operate normally. When I turn the car off then iommeditaely restart (or place the key in position 2) the blower once again does not function.

Alan

Power the blower motor directly ... does it work reliably?

It has a thermal cutout switch built in...

This was not excessive current - only the bad connections at the fuse - when the wires got hot and burned - LESS current was going through them than normal (for sure - or they would not have got hot...). People have a hard time wrapping their heads around this...

Alan

Leon Speed

The resistor pack might be flunky. When I had the same symptoms I discovered a tiny crack in the bakelite plate, causing an intermittent power connection.

Randy V

Could it be the rotary switch in the HVAC control head? Do those fail very often?

Still have to test with 12V direct to the blower motor.

Alan

If the blower resistor pack has an issue it can only affect speeds 0-3, Speed 4 is always direct drive from the switch. On a '94 there is no thermal bypass/cutout in the blower resistor pack like previous years had, also speed 0 is actually Off unlike earlier years.

The blower switches are quite robust so issues are rare (still possible...?) - could also be a poorly seated connector for the switch on the HVAC head.

I think first order is to test the blower motor operation on its own, then if that looks OK test the power on the car side connector with a voltmeter when it seems to be non-operative...

Alan

Randy V

Turns out the blower motor is toast. I also relocated the fuse to an unburned vacant block using heavier gage wire.

Ordered Roger's updated blower kit - looking forward to a cool blow job this summer.

jeff spahn

Randy
How did this turn out? My blower acted up today and I want to check and see how your troubleshooting went.

Randy V

Which part?

I installed Roger's higher rated new blower motor - that fixed the blower problems.

Reference these threads for additional backstory and support:

https://rennlist.com/forums/928-foru...re-w-pics.html

https://rennlist.com/forums/928-foru...retro-kit.html

Shane

I've apparently followed Randy down the rabbit hole...

86.5 5speed. A/C and magic mystery blower syndrome started acting up, and I only had emer defrost and position 4 on the blower fan. Then nothing at all...

I ordered up a new resistor pack and got all the goodies to do Dwaynes write up on the HVAC repair.

I've used deoxit on every connection, fuse, and relay in the CE panel and HVAC system.

Long story short I have found one blown fuse (replaced) and a bad resistor pack (replaced), and though noisy the blower works fine at pos. 4, my A/C is now fully functional again, but no control over fan speeds 1-3.

Is it possible that the blower relay is bad? or is the blower motor shot?

jcb928

How old is the battery? On my old 89 I swapped the resistor & Hvac head with no luck but a new battery fixed the fan not working on 1-3.

Shane

Battery was new in '09, might be something to check on mayhap I need a new ground strap too.

Thanks for the tip James.

Alan

This is not the relay. While it could be the switch it sounds like the switch works for speed 4 - which likely means it works fine - blower switches are rarely any trouble.

What resistor pack version did you install (part #?)? I believe the one for your car is now NLA - the superseeded version is NOT plug & play - you need to swap some connections - if you didn't it wont work.

If the fan worked OK in speed 4: this is simply not a possible fix - something else happend coincidentally. If there are no other symptoms of a bad battery don't mess with it.

Alan