Sigh... Overheating with AC on, bad CCRM?

TIGGER

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This is on my 96 GT vert. I purchased this car super bowl Sunday 2015 from a local tow yard. Car was low mileage but wrecked as it went thru a fence supposedly. Wife drove the car with no real issues for the first couple months after purchase. First real hot day, the wife used the AC and the car overheated. I got it home and looked at it and it appeared that the compressor was seizing intermittently so I told the wife not to use the AC anymore. Unfortunately times were tough back then so it was not till last year that I finally changed the AC compressor. While I was at it, I changed the accumulator, low pressure sensor, and the orifice tube/line. I pulled a good vacuum and charged it. The charge only lasted about a week because the shrader valve from the high pressure side started leaking. I took the dust cap off and it shot straight up. Anyway, I just let it go for the rest of the season. Fast forward to the beginning of this summer, the heater core started leaking. That whole project had major scope creep and fixed the AC again amongst a bunch of other things..

First drive of the day, the AC works perfect and the car does not overheat. If you are running errands, get out for 20-30 min and get back into the car to go to your next destination, the AC does not work and the car overheats. If you let it cool totally down, like let it sit overnight, it works fine again for the first drive. I will add you can tell when it starts wigging out because the car tends to surge or lurch forward kinda hard because it seems like something is putting quite a load on the motor. This is a different surge like when the low pressure switch goes out. It is about twice as hard. Turning off the AC, the surging stops and engine temp goes back down to the R on normal and stays there no matter how hot it is outside. I am thinking that the compressor was an intermittent problem and this issue is what caused the car to overheat 6 years ago on the wife.

Does this sound like a bad CCRM? Any help or advice would be appreciated.
 
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tsemmett

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Is your high speed fan running? A couple years back my car (a 98 GT, so similar setup) would overheat when the AC was running, and I found that the connector to my fan was damaged (one of the pins shoved back out of it), and the high speed fan wouldn't come on. It would behave fine until I turned the AC on, and got it hot enough to be above the range of the low speed fan.

The CCRM itself is just a set of relays; there's not much to it. If something's bogging the engine down, it could be the compressor dragging, or it could be the PCM reacting to being overheated (though mine did not do this when overheating, and it literally boiled over, blowing the water pump seal, at one point).

Were it me, I'd verify both the fan speeds work (you can jump them to a battery for a few seconds on each side to see if they come on). If you want to rule out the CCRM, you could bench test it as well (as I mentioned, it's not much more than a set of relays).
 

TIGGER

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No idea if the high speed fan is running or not. I assume it is on the first start up. I can drive all the way home from work in 100 deg weather (27 miles) with the ac on with no issues. If I run errands is when I see the issue( stop and go). I can be driving it in 100+ With no ac and the car is dead on the R of normal. I can run errands or do whatever. The AC compressor is new btw. How do I bench test the ccrm and the fan? Been trying to find out how but I have not seen specific instructions.
 

tsemmett

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The fan's easy, just run a jumper to ground, and then from the battery to each side of the fan for a moment and see if it turns on. The fan can draw a fair bit of amperage, so use something decent sized (16Ga or bigger I'd say). The wire colors are: Black to Ground, Orange/Light Blue to Hi speed, Red/Orange to Low speed.

As for the CCRM, it looks like you should be able to simply connect the triggers for each relay and check for continuity between each input/output. I'm attaching the pinout and diagrams for the CCRM from a 98 EVTM. There could be some differences between 96 and 98 (for some things I know there are, but I think this is the same), so you might verify the wire colors and such match up.
 

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wmburns

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Does this sound like a bad CCRM? Any help or advice would be appreciated
If this were my car the FIRST thing would be the CONFIRM that the cooling fan actually works on BOTH high and low speed. A non functional cooling fan can make the AC in-op and make the motor over heat.

Also. Don't assume that with the AC on the cooling fan is supposed to run on high speed. For the V8 with the AC on, the default cooling fan speed is LOW. So if the cooling fan doesn't run with the AC on, this means the low speed cooling fan is not working.

If the motor over heats after a ton of stop/go city driving, suspect an in-op high speed fan or clogged radiator.

Don't be a "parts changer". The CCRM is an $$ to change on a guess. Run some tests and then go from there.
 

TIGGER

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I appreciate your input. I have not had a chance to look into this yet. Weather was fairly cool here in Oregon last week. I will go out today and check the fan, it’s on my list of things to do today. But let me clarify some things the car only overheats with the ac on. And it only overheats after I have stopped at a couple stores and shut the engine off and got in and out of the car. If I get in and drive straight home from work (27 miles), after the car has been sitting all day, the ac works fine and it does not overheat. I can be in stop and go traffic too. I just flushed the whole cooling system when I changed the heater core a month or so ago so I think the radiator is fine.
 

wmburns

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So we should assume that the fan will run on both speeds when powered. But do we KNOW IF the PCM has operational control over the fan? This is where a bi-directional ODB2 scanner is worth it's weight in gold. Knowing the answer to this question will take most of the guess work out of trouble shooting if CCRM is good or not.

Here's some information on an affordable ODB2 scanner. A bi-directional ODB2 scanner can be used to COMMAND the PCM to turn on the low speed. IF the fan does not run, then we should suspect a bad CCRM. In the same vein, command the high speed fan to run. Does it run?

Finally some model year Mustangs have a circuit breaker on the low speed fan. If the fan is drawing too much current this could cause the CB to trip. Once the CB cools down it will automatically reset. This could offer an explaination WHY the problem comes and goes.

ForScan ODB2 scanner w ELM327 USB​

 

TIGGER

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Again I appreciate your input. Thank you.

I have the dongle and I paid for the forscan license earlier this year however I do not know what all I’m doing in the software. Ive had it hooked up and dinked around but that was about it. Can you tell me how to check for the pcm operation please?
 

TIGGER

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Now that I think about it more, your circuit breaker theory may hold some weight as it feels like the fan or something is trying to draw a lot of power when the system is acting up because it makes the car jerk when it happens. Turning off the ac makes all that jerking stop.
 

wmburns

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Can you tell me how to check for the pcm operation please?
Have you looked under "activation"?

How about looking through the PID while the motor is running. Some of the PID of interest will have names like "fan speed" or "low speed fan yes/no".

As I said in the informational post I don't use the Forscan software. However during the times I have used it I could always find what I wanted with just a little poking around. But I do agree the Forscan UI is not the most "user friendly".
 

TIGGER

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I’ll try and play around with the software in the next day or two. Not sure if I will have time after work tomorrow.

What do you think about what I said about power draw and jerking? Does that correlate with a bad circuit breaker?
 

manicmechanic007

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It probably does need a new CCRM and or a new connector. I would be looking at the ECT PID waiting for it to get down to .6v (if I remember right). When it hits .6v the processor commands the cooling fan on. You should be able to watch the pin with a dvom. The processor should ground pin 14 of the CCRM when the ECT voltage falls to .6 that turns the fan on.
 

TIGGER

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Thanks for the input, I have not had the time to fool with it the last couple days. Sunday the pass side brake caliper stuck so I have not driven it since. I put used PBR calipers on it 5 or so years ago and now the PBR sticky caliper issue has caught up with me. I will rebuild the caliper and clean it out this weekend and then get back on the AC overheating thing at the same time.

BTW, what is NGS?
 
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