1997 Mitsubishi Eclipse Heater Relay Fuse Keeps Blowing.

BIGTHIN

MEMBER
1997 MITSUBISHI ECLIPSE

Electrical problem
1997 Mitsubishi Eclipse 4 cyl Two Wheel Drive 139000 miles

The heater relay fuse blows once I turn the ignition key on. The heater, a/c, and basically all functions of the system does not work. My question is where to begin looking for the short? I've swapped out the heater relay and that did not change anything. Any help would be appreciated.

5 Replies

KHLOW2008

MECHANIC
41,814 POSTS

Hi Bigthin,

Thank you for the donation.

You should start by unplugging all the components related with the fuse and then with ignition switch on, reinstalling them 1 by 1 till the fuse pops.

If it is Fuse # 11 for the blower motor, then you need to unplug the motor first.

I need to know the specific fuse that is blowing and the full model specifications of your vehicle to get the necessary info on the wiring circuit.

1. Fuse #
2. Turbo or not.
3. Capacity.

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Sunday, October 26th, 2008 AT 7:07 PM

BIGTHIN

MEMBER
3 POSTS

It's the 10 Amp #13 Heater Relay fuse that is blowing when the ignition turns on. I've isolated almost everything, and I found out that when I connect the Automatic Compressor ECM with the ignition on the fuse blows. I've tryed isolating everything associated with the ECM but the fuse still blows. Could the ECM be blowing the fuse? I can't see any damage on the circuit board. It's a 1997 Mits. Eclipse RS 2.0 liter engine. I hope this is enough info for you. Thanks for your help.

Brendan

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Monday, October 27th, 2008 AT 11:29 PM

KHLOW2008

MECHANIC
41,814 POSTS

Hi Brendan,

Ok, I got the fuse and the circuits that uses it.

Here are a list of items associated with the auto compressor ECM
1. Dual pressure switch
2. A/C switch
3. fin thermo sensor
4. Compressor revolution pickup sensor
5. Defroster switch
6. ECM (Engine)
7. Compressor
8. Condenser fan relay.

If you have not tested any of the above, might as well give it a try. The compressor is the most likely item as it has a higher possibility to cause shorting. However with AC switch unplugged, it should not cause the shorting.

It is possible for the ECM to short internally as there is a ground wire from it.

The data above are for a non turbo automatic, so hope it is the correct vehicle and let me know if you are able to solve the problem.

Good luck.

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Tuesday, October 28th, 2008 AT 12:05 PM

BIGTHIN

MEMBER
3 POSTS

I ended up pulling all the wires out of the Automatic Compressor ECM. I installed only the hot wire and when I installed the ground wire with the engine running it blew the fuse. I found that one of the resistors on the ECM has a direct short going through it. I can't find anything on the internet about replacing the Automatic Comp. ECM. Any ideas and pricing about getting a replacement? Thanks for the help.

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Wednesday, October 29th, 2008 AT 12:23 PM

KHLOW2008

MECHANIC
41,814 POSTS

Hi Bigthin,

Sorry I don't have any info where to source the item.
Since you have isolated the source, you can try replacing the resistor if soldering can be done. The resistor should be availble at electronics parts stores and would not cost you more than a buck each.