No Heater or AC fan

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dks
Posts: 29
Joined: Mon Sep 30, 2013 11:56 am
Location: Brisbane, Australia

No Heater or AC fan

Post by dks »

G'day - need a bit of help.

It's 35C here in Brisbane and there is no AC fan at all (or heater fan either) - at any setting, max too.
AC light comes on when the button pressed.
No fuses gone - I've seen that Brucey says don't necessarily believe the documentation for fuses on RHD cars - so check them all.

I've checked out the '87 ETM and understand how the AC & heater bits work.
It says I need to run tests on (H) the Heater Final Stage voltage regulator, (I) the AC Final Stage voltage regulator and (J) the blower selector relay.

I know where the first two are (not real keen on getting to the AC one) but no idea where the blower selector relay is on a RHD car. Everything suggests it is next to the glove box but methinks that is for a LHD car.

Can anyone give me a clue before I start ?

My first thoughts are it is the Blower Selector Relay but I did a quick continuity check from the ground side of the heater blower motor to earth - about 1ohm. So, I ain't so sure any more but I need to go through the tests.

I had the AC working nice (about 5-6C at the vent) so any suggestions most welcome.
'87 635
'84 323
Pod
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Re: No Heater or AC fan

Post by Pod »

No doubt you know that if the aircon button is operated, the aircon fan will start and the “normal” fresh air fan will stop. There may be a conflict and I would start here if I were you. Try disconnecting the aircon button for starters and see if the fresh air fan starts working? Good luck!
dks
Posts: 29
Joined: Mon Sep 30, 2013 11:56 am
Location: Brisbane, Australia

Re: No Heater or AC fan

Post by dks »

G'day Pod.

I did understand the switching of blowers - but it always good to get another opinion so thanks for the reply.

The AC switch is one of the common points - and where I was going after the blower selector relay.

I thought the AC switch worked - I could hear the compressor clutch kick in and also the light went on - so that was 2 of the 3 legs on the AC switch working okay.

Turns out the blower selector relay was just fine (at least when I took it out and checked it) but when I connected it all up again the AC selector switch wasn't happy - no compressor clutch engagement or light. Gave it a good clean (not real bad to start with) and put it in again - lasted only a couple of presses before giving up. It looks as clean as but something is wrong.

I'll jumper the AC switch connections and see what gives as the next step.
'87 635
'84 323
DrTwincam
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Joined: Mon Apr 29, 2019 3:58 pm
Location: GA, Jawjuh - California

Re: No Heater or AC fan

Post by DrTwincam »

The ac switches can fail at first intermittently, then gone. That is a 30 amp circuit as I recall. The switch may appear to be clicking into the closed circuit position when it is not. Simply pull the switch and use a jumper wire w 30, 87, etc. I would not rule out the fuses unless you are using a test light and are on the backside of each of the brass showing power on both poles to ground. Always a good thing to give each of them a spin while in there.. Is the compressor clutch engaging? Compressor turning? Also, with the ac switch in the on position, you should have power down at the large temp switch at the bottom of the radiator. If you jump those two wires the fab should kick on.
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dks
Posts: 29
Joined: Mon Sep 30, 2013 11:56 am
Location: Brisbane, Australia

Re: No Heater or AC fan

Post by dks »

I sorta ruled out the AC switch initially because the blowers didn't work on max and this pretty much bypasses the AC switch (except for the blower selector relay needing input from it)

I think I'll jumper the blower selector relay to check max operations of both fans without the AC switch.

Take you point about fuses - I'll check both sides.

Compressor and clutch have been good. I'll jumper each of the pins on the AC Selector switch to make sure they are all doing their bit.

I can see the circuits for the aux fan and the temp switch - I'll check them too.
'87 635
'84 323
dks
Posts: 29
Joined: Mon Sep 30, 2013 11:56 am
Location: Brisbane, Australia

Re: No Heater or AC fan

Post by dks »

G'day folks.

I've finally gotten back to this perennial problem...

So, to the best of my reconning
- fuses 19 & 20 are good
- blower select relay is good - exactly same results when I use jumpers

I strarted to run through the '87 ETM for Heating and AC - need to run tests G, H & J, G & I, I & J for the blower fans not working at all for heating or cooling.

For test G table 1, too hard to get at the back of the Blower Speed Control, so went to test G table 2 - measuring volages at the AC selector switch

For the 5 tests I get the following

AC Selector Switch disconnected
Blower speed: slow
5&Gnd, expect <0.5v, actual .06v, Pass
Blower speed: fast
5& Gnd, expect ~10v, actual 18mv, Fail
AC Selector Switch reconnected - OFF
1&Gnd, expect ~10v, actual 2mv, Fail
AC Selector Switch reconnected - ON
3&Gnd, expect ~10v, actual 52mv, Fail
Blower changed to slow
3&Gnd, expect ~3v, actual 0.6v, Fail

To me this all points to a cactus Blower Spped Control - or am I missing something by not doing the table 1 test

Anyone got any ideas or further suggestions
'87 635
'84 323
emac
Posts: 178
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Location: SC

Re: No Heater or AC fan

Post by emac »

I am having similar problems, please post if you find a solution.
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