EATC problem

[BaySHO Performance]

Problem: blower motor comes on when the ignition is turned on before starting the engine, even though the EATC is off. Can’t get the blower to turn off.

Background: ’95 MTX, 155K miles. I drove it home from the client’s house, everything was working fine. Replaced the radiator as preventative maintenance (disturbing the D code CCRM which is included in the AC circuit), and resealed the oil pan. New jiggle valve thermostat also installed. Put radiator flush in it and ran the engine with the heater set to 90. Ran it until the thermostat opened and topped it up until no more air came out (so no low coolant). Then ran it for a further 10 minutes per instructions.

While the engine was running, I noticed that the AC compressor was operating even though set to 90, and the fan was running (presumably because the AC was on). Turned the engine off, but now the blower comes on with the ignition turned on but engine and EATC off. Can’t remember whether it was doing that when I initially started the car. I don’t think so.

EATC working fine apart from not turning off. Register selection OK, blowing hot or cold depending on the temp setting, blower motor speed varies with thumbwheel. The only oddity is that if I go to ‘MAX AC’ and then set the temp to 90, the ‘MAX AC’ indicator is still lit.

Tried replacement CCRM: no difference. Its wiring looks fine. Battery voltage OK. All fuses fine. No engine codes.

Ran EATC self test on a warm running engine. Came back with 888. Gets generated if:

- Vacuum system inoperative (it’s working fine)

- AC not working (it is)

- Bad CELO switch: Cold Engine Lockout / Temp Control Lockout Valve in one of the tubes going to the heater core. Stops the blower motor coming on until the engine is hot enough to warm the interior. I disconnected the CELO switch and turned the ignition on: no difference. Same with disconnecting the ECT sender. No pinpoint test for this problem in the manual.

Has anyone come across this problem before? My best guess is that the CELO switch got clogged from all the gunk loosened by the radiator flush. Another possibility is that the EATC got damaged by setting the temp to 90, but that’s a long shot.



Thanks

Nick

 

[sperold]

Does the rad fan motor shut off after a few minutes (or seconds) when you first turn the key to on?
My 90 fan runs for 10 seconds when I first turn the key on, but shuts down by itself. If I start the car and have it running, it still shuts down by itself.
It has done this for years.

Did you disconnect the connector on your CCRM. If you did, maybe disconnect and reconnect that plug a few times

As far as I know, if the air conditioning is set on max air, the compressor is always running, no matter what the temp is set at.

Vacuum tubing leaks are almost always the reason for codes on the self test of the EATC.

Some funky symptoms that are classic CCRM symptoms can be caused by a bad ground in your ECM unit, so check the ground pins on that hard to access connector.

 

[BaySHO Performance]

Thanks for the reply. Fan stays on all the time with the engine running, as does the AC, which is presumably why the fan is on.

Disconnected the CCRM, cleaned the contacts with electric component spray, tried known good CCRM, no difference.

Hmmm. Maybe the MAX AC light was on all the time because I didn't turn off MAX AC before I went to 90.

Can't be any vacuum leaks as the air comes through whatever register I select.

ECM? Are you referring to the ECU/PCM?

I'm going to try a replacement CELO switch and ECT Sender tomorrow.

 

[sperold]

My money is on ground circuits if the fan stays on all the time, I have heard a theory that the unit grounds itself through the CCRM relays when the grounds get weak, but that might be a myth.

The first ground I would check would be the CCRM main ground at your disturbed connector, it is Pin #15 and is BK / LG wire colour. It goes directly to ground.
I would run a new wire from the battery negative post to this wire and see if things improve. The other 2 grounds from this unit are the fuel pump and the rad fans, and both of them seem to be fine.

Your CCRM itself is OK if you have swapped it out and nothing changed.

You will need an Electrical and Vacuum Troubleshooting Manual (EVTM) to make any sense of the grounds for the CCRM and the connections to the PCM.