HVAC Heater Blower Problem: Not Relay or Motor or Resisitor

Dynamic Entry · Post by **Dynamic Entry** » Thu Apr 10, 2008 3:30 am

Ok, my heater blower was being tempermental months ago and completely quit weeks ago. I have been searching and reading, tearing my interior apart, cutting my hands & swearing. You guys know the drill

I did in fact check all my fuses by the pedals and in the engine bay. All were good.

From what I have read there are 4 main components that can impede the functioanlity of the blower: Relay, Resisitor, Motor and HVAC Control unit

Resistor - I have so far counted this out because when the fan stopped blowing it wouldn't blow on any of the 4 levels

Motor - I never suspected the motor because it worked off and on, and never showed signs of having trouble starting if it worked. Before pulling my relay I checked the plug going into the motor and there was no voltage there. I checked my parts car plug the same way and it showed 11.83 Volts
That being said, so far I have NOT checked the motor with jump wires (because I have reason to believe the problem is somehwere else)

Relay - I suspected the relay from the start because of the above reasons. I spent a full hour digging around last week and failed to locate the thing. Today I spent 2 hours between my SS and parts car.
I was so happy when I finally got my known working spare relay into my SS and SO sad when it didn't do anything!
I have confirmed that both my relays work fine. I used a jump wire to bypass the relay in my parts car and had success. Jumping the SS does nothing, and with either relay there is still no voltage at the motor.

HVAC controls - I have not pulled this out, not checked the soldering or the plug. Doing that is my next step. Could the controls be the place where the circuit is being broken?

Other - I read other posts about aftermarket cruise and fog lights (and probably alarm systems) being tapped into the wiring at the fuse box and shorting out, causing failures like this. I have an alarm system that was giving me problems that I have disconnected. I will also pursue this in case there is some connection.

Dynamic Entry · Post by **Dynamic Entry** » Sat Apr 12, 2008 12:31 am

I had a phantom today.

At some point yesterday I blew a fuse. My Temp gauge, tach, power windows, HVAC power all cut out.

It is labelled Meter on my fuse box cover.

After replacving it and regaining power to the HVAC controls, power window and gauge functionality I decided to re-check the connection at the blower motor.

I took a reading and it had 12 volts. So I figured I had been wrong all this time and pulled the motor out of my parts car.

But it was just a phantom. The known working motor didn't run. And when I rechecked there was no voltage at the connection.

So, there is a problem inbetween the relay and the motor. I guess I am pulling my dash apart next to check the controls

stipro · Post by **stipro** » Sat Apr 12, 2008 5:51 am

Ok, try this.

First check pin 2 + 4 at the realy conn. for corrosion, or heat damage to the wires. Just insure they look to be in good shape.

At the relay conn. jumper across pins 2 (red /yellow) and 4(black/red), check to see if the fan motor works from low to high on the fan switch.

If everything works than you know that blower motor, resistor, and fan switch work.

At this point, you are assuming that the relay is good. Now, with the ignition switch on, see if you have 12v at pin number 1(red/black) and a body ground, on the relay conn. If so test across pins 1 (red/black) and 3 (green/black) and the volt meter should change.

If not, than there is an issue either with the wire at pin 3, between it and the mode control panel, or the control panel itself. Do a cotinuity test from pin 3 on the relay conn, to pin 6 (green/black) at the mode control panel, if you have continuity, than the mode control module is bad and replace the HVAC controller.

Note: The mode control panel is part of the Hvac controller.

Dynamic Entry · Post by **Dynamic Entry** » Sat Apr 12, 2008 8:28 pm

thanks Mike. I will try all that tomorrow

Dynamic Entry · Post by **Dynamic Entry** » Fri Apr 25, 2008 8:32 pm

stipro wrote:Ok, try this.

First check pin 2 + 4 at the realy conn. for corrosion, or heat damage to the wires. Just insure they look to be in good shape.

At the relay conn. jumper across pins 2 (red /yellow) and 4(black/red), check to see if the fan motor works from low to high on the fan switch.

If everything works than you know that blower motor, resistor, and fan switch work.

At this point, you are assuming that the relay is good. Now, with the ignition switch on, see if you have 12v at pin number 1(red/black) and a body ground, on the relay conn. If so test across pins 1 (red/black) and 3 (green/black) and the volt meter should change.

If not, than there is an issue either with the wire at pin 3, between it and the mode control panel, or the control panel itself. Do a cotinuity test from pin 3 on the relay conn, to pin 6 (green/black) at the mode control panel, if you have continuity, than the mode control module is bad and replace the HVAC controller.

Note: The mode control panel is part of the Hvac controller.

Ok, I am back to being confused.

The pins and wires look great, no reason to suspect a problem at these terminals.

I jumped pins 2+4 (thicker gauge red/yellow & black/red) for redundancy sake (cuz I know my relay works in the other car) to no avail

But when I check continuity pin 1 to ground gives 11.8 volts and across pins 1&3 gives 9.8 volts

So there is voltage going to the relay for sure.

I plugged my known working spare blower motor in and there is no response.

I checked at the motor harness again and there is nothing there. 0.2 volts

I didn't check the HVAC controller because your instructions said to do so if there was a problem with voltage at the relay conn. and there is no problem there.

So i have a problem inbetween my relay and the motor. Is there anything between these two besides wiring?

Dynamic Entry · Post by **Dynamic Entry** » Fri May 02, 2008 7:46 pm

So I pulled my HVAC controller out, I was hoping to swap in my controller form the 90L but found out that they are not compatible....

I also checked for voltage at the harness that plugs into the fan speed selector. I wasn't able to find any.

make me think that the problem is in the wiring between my relay and hvac controller. that doesn't seem nice.

onetwistedwreck · Post by **onetwistedwreck** » Wed Dec 03, 2008 5:15 am

please do not end this thread this way because I am in the same boat as you are or was, so please let me know what you found out.!! I see this is a old thread so I'm also going to pm you if you dont see this post. I am going to go and try what stipro has suggested see what I find. I tell you what, if I get much deeper into this I swear I'll be coming out the engine compartment through the fire wall

tahiti350 · Post by **tahiti350** » Wed Dec 03, 2008 5:22 am

every time I've had intermittant or total failure of the heater it was the control panel. It's easy to swap out, and only takes a few minutes. I also keep spares around, just in case.

93forestpearl · Post by **93forestpearl** » Wed Dec 03, 2008 9:46 pm

My sedan went through relays about once a year. I'd still hear it click, but it didn't work.

On my beater wagon, I swapped everything out, aside from the fan and that didn't work. I went to change the fan and found that the connector for the fan was roasted. Replaced it and problem was solved.

nottofast · Post by **nottofast** » Thu Jan 08, 2009 2:32 am

I have the same going on with 91ss. Heater fan works intermittantly. Keep pushing different buttons. Does anyone know if 93SS will work? I have a couple of those switches sitting around.

Hmm....maybe I will check the fan and connections first.

Dynamic Entry · Post by **Dynamic Entry** » Fri Jan 09, 2009 9:43 am

the pre and post facelift HVAC control units are not interchangeable

nottofast · Post by **nottofast** » Fri Jan 09, 2009 6:48 pm

Dynamic Entry wrote:the pre and post facelift HVAC control units are not interchangeable

Thank you. I also have a 91 FWD car I can get parts from then. You saved me time friend. J.

guesswho · Post by **guesswho** » Sun Jan 11, 2009 5:27 pm

Dynamic Entry wrote:the pre and post facelift HVAC control units are not interchangeable

They're different? Are you talking about the HVAC box that sits behind the dash or the control piece that has the buttons to adjust the fan. My 91SS fan is acting weird and I think I have a similar problem.

log1call · Post by **log1call** » Mon Jan 12, 2009 7:49 am

They have a diagnostic feature and you should be able to get trouble codes out of them. If you go to... http://www.subaru-svx.net/forum/forumdisplay.php?f=5 there is a section called "how to" which has an aircon section with fault finding and diagnostic code extracting. You might have to register.

justin the subie · Post by **justin the subie** » Wed Jan 14, 2009 12:21 am

93forestpearl wrote:My sedan went through relays about once a year. I'd still hear it click, but it didn't work.

On my beater wagon, I swapped everything out, aside from the fan and that didn't work. I went to change the fan and found that the connector for the fan was roasted. Replaced it and problem was solved.

mine has been really funny!! it will work if the car is warm for whatever reason!!i have tried changing everything.. but im not sure where the fan motor relay is.. help??

Dynamic Entry · Post by **Dynamic Entry** » Wed Oct 28, 2009 3:51 am

Oh how I wish I was resurrecting this thread for different reasons.

Sparing details I will say that I didn't drive my car last winter, but will this coming winter and so have dug back into it.

Above I mention that jumping pins 2 & 4 previously did NOT successfully operate the blower.

Last week when I tried the same thing it DID work.

This made me feel both happy and sad. It was nice to get a response but made me wonder if I could have made a mistake the last time.

So I just said whatever and ordered a new relay from the dealership.

For the week+ it was on order I happily drove around with a jump wire in the place of the relay and my HVAC worked flawlessly the entire time.

The day my relay came in I drove there with the defrost blaring. I came out of the parts dept (after a typical lengthy process) and removed my jump wire, replacing with the new relay (which has the same part # on it as my old one).

Nothing.

Put my jump wire back in.

Nothing.

Had blown the 'Meter' 10 amp fuse (windows are also on this circuit).

Replaced fuse. Then put new relay back in.

Nothing.

Relay out and jumped across 2 & 4 with car ON and watched the fuse blow.

Repeated above process twice more since I had more fuses and I was angry.

So as it stands I have two (2) good relays, two (2) good HVAC controls, two (2) working motor/fan units and no (0) easy solutions

I assume there is a short somewhere?

tahiti350 · Post by **tahiti350** » Wed Oct 28, 2009 9:38 am

I've had the same problem on all 3 wagons, and each time it was the control panel... my '90 LS has a piece of cardboard pushing the control panel connection up slightly and has worked that way now for over 2 years... That would be bad solder joints at the panel connector.

Dynamic Entry · Post by **Dynamic Entry** » Sat Oct 31, 2009 9:55 am

I know the control unit cold soldering has been the culprit for many people. It isn't the point of failure in my case. I've bought replacement units and opened some up.

Also, it has never been a problem in selecting modes or levels. It has always been a complete failure issue that has been positively linked to the relay wiring.

I am going to dig deep into the guts tomorrow. Hopefully I will come up with better understanding, and best of all a solution.

DannycVR6 · Post by **DannycVR6** » Fri Feb 19, 2010 3:39 am

did you ever find anything?

i have the exact same problem.. also where is the fan control relay?

Dynamic Entry · Post by **Dynamic Entry** » Sat Feb 20, 2010 6:18 pm

uhhhmmm, my 'solution' in the end was to remove the relay entirely, jump pins 1 and 3 and increase the fuse from a 15 to a 20 amp...

no fires so far.

diagram of location, cheers to Josh!

DannycVR6 · Post by **DannycVR6** » Mon Feb 22, 2010 3:58 pm

Dynamic Entry wrote:uhhhmmm, my 'solution' in the end was to remove the relay entirely, jump pins 1 and 3 and increase the fuse from a 15 to a 20 amp...

no fires so far.

diagram of location, cheers to Josh!

found the relay last night what a nightmare to get to.
the relay socket and the pins on the relay its self are discolored from heat it looks on the 2 switch terminals.

Dynamic Entry · Post by **Dynamic Entry** » Mon Feb 22, 2010 4:26 pm

DannycVR6 wrote:what a nightmare to get to.

truth

In a way finding heat discoloration could be encouraging? In that you may have found the problem. I never figured out what my problem was.

But wiring on a new harness doesn't sound particularly happy.

So but first you get to try a new relay and see what happens, ya?

DannycVR6 · Post by **DannycVR6** » Mon Feb 22, 2010 11:22 pm

looks to me like the contacts in the relay couldn't handle the current and oxidized due to the heat and age which created even more resistance...?

I think for now I'm going to jump the relay socket.

If that doesn't work I may add an extra switch.

If that doesn't work I may wire a new larger relay in.

Post by **Legacy777** » Tue Feb 23, 2010 12:46 am

Why not just get another relay? Even if you just get a generic one and rewire the plug.

DannycVR6 · Post by **DannycVR6** » Tue Feb 23, 2010 5:10 am

Legacy777 wrote:Why not just get another relay? Even if you just get a generic one and rewire the plug.

its not the relay...

Just tested it there it works fine with power on the coil.

Tested the relay socket there is no power on the coil poles.

Update: it works now it is a bad relay socket

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HVAC Heater Blower Problem: Not Relay or Motor or Resisitor

HVAC Heater Blower Problem: Not Relay or Motor or Resisitor