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Heater Blower out - is there a relay? 700 1991

posted by turboct on Fri Jan 30 07:37 CST 2009
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last visit: Tue Oct 15 19:03 CST 2013

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Hi All,

My 91/750T/185Kmile heater blower isn't running - just as we are in the thick of winter here in CT! Hoping you have some ideas to look for because I'm getting cold fast!

Situation:

- replaced the blower last year/this time (new from FCP)
- has been running on position 5 only since last fall indicating heater resistor pack failure per FAQ
- today doesn't blow at all (but car runs/temp normal)
- checked Heater 30A Fuse #6 per diagram and it looks ok
- I have not pulled the CCUnit (though did replace with good/used 2yr ago)
- I have not pulled the fuseblock to look at underside

Is there a Heater Relay somewhere I'm missing? I couldn't find it on the FAQ diagrame and have searched the forum - no mention save for seat heaters. If there's one hidden away I'd love to check that (I've been repairing those under the hood, could it be one of them)?

Any points in particular you'd suggest checking?

Lastly, is there a USA source for the heater resistor pack other than the dealer (FCP doesn't seem to have them on their website)?

Many thanks in advance!

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No relay, but fuse # depends on CC type. 700 1991

posted by lucid on Sat Jan 31 01:53 CST 2009
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last visit: Fri Oct 24 12:31 CST 2014

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On my '93 940 (with MCC), the blower fuse is #16. The factory diagram shows fuse #6 is for the ECC version. My '93 diagrams don't show a fuse 28.

If you have the 1-5 fan knob, you have the MCC. The fan is controlled Electronically with ECC, according to the diagrams.
--
Bruce Young, '93 940-NA (current), 240s (one V8), 140s, 122s, since '63.

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No relay, but fuse # depends on CC type. 700 1991

posted by turboct on Sun Feb 1 08:38 CST 2009
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last visit: Tue Oct 15 19:03 CST 2013

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Follow-up: Immediate problem solved. Indeed Fuse #16 was blown and replacing it powered up the blower and brought back warm air! Hopefully this will hold me until I can dig into the resistor pack problem (and get back 1-4 speeds).

I guess I had not read the full listing of fuses and didn't realize there may be another involved. The Fuse list on the ash-tray says for #6 "(Heater Fan ECC)/30A" while for #16 "(Climate Control ECC) (Heater Fan/Air Cond MCC)/30A". As mentioned previously, #6 was ok whilst #16 blown.

Thx Lucid and all!

Lewis in CT

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Heater Blower out - is there a relay? 700 1991

posted by turboct on Fri Jan 30 10:00 CST 2009
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last visit: Tue Oct 15 19:03 CST 2013

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Opps - my bad typo. What I have is a 1991 740 Turbo. I was hoping to check out the easy/accessible items before I go do another part-dig. At least now I know there is no heater-blower relay.

I don't know if this makes a difference, but from the fAQ - it says the resistor pack is essentially by-passed when the fan is on position 5 (the highest setting) to allow max current. Again this is what I've been using since the pack failed sometime last fall (I've been having to run the blower on full blast, then shut off when getting too hot inside the compartment). I suppose that could have stressed the switch..but we shall see when I can get the fan dug out/tested and work backwards from there.

still looking for a USA-non-dealer source for the resistor pack if anyone has any suggestions.

Thx.

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Heater Blower out - is there a relay? 700 1991

posted by porkface on Fri Jan 30 08:01 CST 2009
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last visit: Fri Oct 24 09:12 CST 2014

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you posted 91 750t-i'm ASSUMING 760t. if it's a 740t, post a correction.

there's no relay. power comes from fuse 28 and it's powered by the ignition switch. so is there 12v at the blower? use a meter, a test light will work with 8 volts, too. if not, go back further until you get 12v. a worn out ignition switch or a melted fuse box will cause 12voltus interuptus. if 12v at the blower, run a ground wire from the blower as a test. if the blower runs, you need the resistor/controller on the case or the acc controller in the dash is fried and not sending the resistor it's signal to run the blower. VERY COMMON on the 850's the get a blower, resistor and controller. never had to do that with a 760, replace the blower OR the resistor/controller OR the acc controller. good luck, chuck.

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Heater Blower 700 1991

posted by B.B. on Fri Jan 30 22:26 CST 2009
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last visit: Mon Oct 6 13:15 CST 2014

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Well said Porkface.

You can get a resistor pack at a boneyard, but it's prudent to
check out the ignition switch and see if there's 12 volts at the fuse
(under load/fan on). You may also have a bad ground connection and or connection to the resistor pack. Get your meter out to pinpoint where you lose 12Volts and or the ground connection.

Bill

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