Temp Goes Up With AC

[Midnight Specialist]

I recently had my R-12 system charged up and when the AC is running the temp climbs to 220 (and over, if I don’t turn it off) once I turn it off, goes back to a little over 160. This happens no matter how I’m driving and with fans on (upgraded fans from delorean parts northwest). I have Dave McKeen’s relays and electric otterstat as well.

I got the air out of the system with the delorean parts northwest bleed kit and still happens. Any ideas on why this is? Could it be just the heat? Been in the upper 90s here in mass.


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[Bitsyncmaster]

With AC on your fans are running all the time so my guess would be the radiator is not cooling enough. If you have already flushed it and verified your water pump is working, I would think about replacing the radiator.

[WHO1DMC]

I recently had my R-12 system charged up and when the AC is running the temp climbs to 220 (and over, if I don’t turn it off) once I turn it off, goes back to a little over 160. This happens no matter how I’m driving and with fans on (upgraded fans from delorean parts northwest). I have Dave McKeen’s relays and electric otterstat as well.

I got the air out of the system with the delorean parts northwest bleed kit and still happens. Any ideas on why this is? Could it be just the heat? Been in the upper 90s here in mass.


Sent from my iPhone using Tapatalk

Possible air flow problem. How clean and open are the fins on condenser and radiator?


Dave B.

[Midnight Specialist]

The radiator is less and a year old and I’ll have to double check the fins on the compressor.


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[JBaker4981]

What is the possibility that it could be overcharged? I'd think in that scenario that the engine would have to work a lot harder to turn the Compressor pulley.

My car potentially is experiencing this scenario when on the interstate as it can get to 220 before I shut off the AC and like you, I am running almost everything new for the cooling system. DPI Fans, DPI Radiator, Rebuilt Water Pump, McKeen Relays, etc. (No, there is no air in the system)

[David T]

The cooling system should be keeping the motor around 180, not 160. Either you have the wrong thermostat, it isn't working correctly, or you are not measuring the temperature accurately. If the temp goes way up with the A/C on, either the fans are not working correctly, not enough air flow, or the A/C system is not right. Is the compressor cycling?

[cdrusn]

Just bypass the otterstat to keep the fans running continuously so you can finally get over the question "are my fans coming on as they should". Once you know the fans are on all the time you can spend your energy looking for other possible solutions. Does it get hot in traffic? Does it run cool on the freeway?

[artisticent]

What is the possibility that it could be overcharged? I'd think in that scenario that the engine would have to work a lot harder to turn the Compressor pulley.

My car potentially is experiencing this scenario when on the interstate as it can get to 220 before I shut off the AC and like you, I am running almost everything new for the cooling system. DPI Fans, DPI Radiator, Rebuilt Water Pump, McKeen Relays, etc. (No, there is no air in the system)

Is that a thing? If the AC system is overcharged the engine will have a harder time turning the pulley of the AC Compressor?

[David T]

Not only is it hard on the motor, It is deadly to the valves in the compressor.

[artisticent]

Not only is it hard on the motor, It is deadly to the valves in the compressor.

wow good to know. Youd think the system wouldnt be able to take more than it can handle. I drained my system entirely and than ran vacuum on my system for an hour or so to burn any moisture. Then I used a can of the redtek stop leak and it took 2 more cans of refrigerent. It blows cold and works perfectly. Slight loss in horsepower that i notice on acceleration but overall everything is good. Wondering if I should connect the gauge manifold to the white cap connector and measure the pressure again

[David T]

If you filled it with the correct amount of refrigerant (2.2 LBS of R-12), the gauges will only tell you if you have non-compressable gasses and the low pressure switch settings. If it is cycling like it should you should be fine.

[JIMJAM]

People up N park during the brutal winters, I park during the brutal summers. My D has always hated summer and when all my issues pop up.
Once that stainless heats up, no break from the sun and parked on black top, the car cannot take it. I had to get accustomed to a engine that after shutoff can be burn your hand hot 4+ hours later.
Even with a upgraded radiator, custom fans, air dam to block fan heat from the tank, upgraded stainless bottle with 3 auto bleeds and a sensor that turns on the a/c fans sooner, my indicated temp on the dash has always hung betreen 220 and the next bottom line. Over 90 and real sunny the needle sits just under the 220. Threw all this money at it and that where it still sits even with all the mods.

Thats been my "normal" temp for 20 years and seeing that the engine hasn't melted either the gauge is wrong or the car can operate at that temp. Now if it starts touching that line and I am highways speeds, ok... But if I run across a traffic jam it's time to park under a overpass which I have done.

[JBaker4981]

Following up!

My car is still experiencing this issue. At our Tech Day last weekend, we replaced the low pressure switch (DGo) and dialed it back a full rotation counter clockwise as per their instructions for R134a. We verified that my system was not overcharged but undercharged so we added enough to verify that both High and Low sides were within spec with the ambient temperature that day.

While the AC is super cold and a blessing, my car still wants to overheat with the AC on while on the interstate/highway.

Now... On these early summer days with the outside temperatures being ~85F, I can drive the car around town, sit in traffic, and drive normally like any other car without issue with the AC running. The temperature gauge stays at the quarter mark in these scenarios.

But... If I hop on the interstate or a highway where I am driving consistently above 55mph with the AC on, then the temperature gauge starts creeping up to 220.
68413

When it gets close to 220F, I can turn it off and it will gradually creep back down to where it likes to sit. (Picture below is after it started creeping up once I turned the AC back on, but you get it)
68414

With the AC off, even on a HOT day like 90-100F (example such as last summer), the car stays cool.... around the 175F range. No joke - it sits a needles width above the first white line on the gauge. With that said, I think my cooling system is working well and the culprit has to be the AC system. (Picture from a hot September 2020 day)
68415

I am currently rocking:

DPI 2-Stage Aluminum Radiator
DPI Fans
Rebuilt Water Pump
R134a Conversion
New Low Pressure Switch
AC Compressor - Unknown Model (IE Not Sanden)


Fans, Radiator, & Condenser below
684176841668418

Anyone have any thoughts? I would like to get this sorted out and actually enjoy the car with Summer rapidly approaching and Ceramic Tint now on the car.

[David T]

It can get complicated because you need 2 systems to work well, the cooling system AND the A/C. I like to start with the cooling system. I see you have done a lot to upgrade the cooling system. There are some things you still can do. Check the timing, vacuum advance and mechanical advance of the ignition system. If it is not right the engine will run hotter than it should. Calibrate the temp gauge with an IR thermometer. Verify both fans run and are running in the correct direction. Make sure NOTHING is blocking the intake grill for the rad like a license plate. Test or replace the thermostat. See if any of this makes a difference. Once you can get the cooling system to run right the A/C system may not need any work.

[Bitsyncmaster]

With it running hotter with the AC on you have verified that the problem is not the otterstat since the fans run all the time with AC on. Your air flow is the same over both the condenser and radiator so that is not the problem. But the AC pre-warms the flow over the radiator. So what I would do is a flush of the engine coolant with my guess you have poor heat transfer from the engine block to coolant.

Use a radiator type flush that removes contaminates and oxidation.

[Jason]

Maybe check for exhaust gases in the coolant?

My car would behave similar to what you describe. Normal temps with the AC off, but with the AC on and over 80 degrees outside the coolant temp would just slowly rise, even when driving at highway speeds. Turned out I had a head gasket leak that was letting some exhaust into the coolant which lowered the cooling efficiency just enough that it couldn't keep up when the AC was on. Other than the AC temp problem and that an exhaust gas in coolant test read positive there were no other symptoms.

[Ron]

What's bugging me here is that the thermostat shouldn't let the temp drop below 195° F, and, 220°F is acceptable.
Not to mention that the gauges are not known for accuracy.

But I have to agree with Dave WRT the cooling system being able to handle anything the AC can throw at it, and then some.

[FABombjoy]

What's bugging me here is that the thermostat shouldn't let the temp drop below 195° F (180°F if no converters), and, 220°F is acceptable.
Not to mention that the gauges are not known for accuracy.
On my car the temp gauge is very nonlinear after the first 1/4 mark when compared with the EFI temp sensor. This might be "solving the gauge" rather than "solving an overheat".


But I have to agree with Dave WRT the cooling system being able to handle anything the AC can throw at it, and then some.
As long as the ducting is installed and the fans running, for sure. I see that the plastic fan shroud has been replaced with metal, which I'm not a fan of (oops, pun). Is the original ducting still in place? My experience with fan shutdown at speed shows that passive airflow is bad, so all of the pieces really need to be there for things to work the best.

[FLUX @88]

I have the same issue, I am going to flush my coolant again as I noticed in the jar some crude. My radiator is also a year old... I have a feeling some crude has made it was in the radiator.....

[cis6409]

Maybe check for exhaust gases in the coolant?

My car would behave similar to what you describe. Normal temps with the AC off, but with the AC on and over 80 degrees outside the coolant temp would just slowly rise, even when driving at highway speeds. Turned out I had a head gasket leak that was letting some exhaust into the coolant which lowered the cooling efficiency just enough that it couldn't keep up when the AC was on. Other than the AC temp problem and that an exhaust gas in coolant test read positive there were no other symptoms.

+1 for me to.. - (IF all the other things check out like both fans working ETC) . The A/C making it go hotter seems to be more of a symptom not the cause. It's exposing a weakness in the cooling system by putting more 'stress' or load onto it that it can otherwise handle.
Hopefully it's not that for you good luck witb the investigating

Shane

[Helirich]

What's bugging me here is that the thermostat shouldn't let the temp drop below 195° F (180°F if no converters), and, 220°F is acceptable.
Not to mention that the gauges are not known for accuracy.

But I have to agree with Dave WRT the cooling system being able to handle anything the AC can throw at it, and then some.

Yea, this has me thinking. My car runs cooler with the AC on. I think it’s be cause the fans run all the time. Makes me think my thermostat is no good. (Or missing) Of course this is not as serious as overheating, but probably hurts my mileage.

[Bitsyncmaster]

Yea, this has me thinking. My car runs cooler with the AC on. I think it’s be cause the fans run all the time. Makes me think my thermostat is no good. (Or missing) Of course this is not as serious as overheating, but probably hurts my mileage.

There was an otterstat that turned at a lower temp that Hervey use to sell. I had one on my car and the fans kick on just a hair above the 1/4 mark. I now have the screw in otterstat and it kicks on at the same point. It is critical your temp sender for the gauge be the correct one to get proper readings on the gauge. I did testing on the temp senders somewhere posted on DMCtalk.

[David T]

There was an otterstat that turned at a lower temp that Hervey use to sell. I had one on my car and the fans kick on just a hair above the 1/4 mark. I now have the screw in otterstat and it kicks on at the same point. It is critical your temp sender for the gauge be the correct one to get proper readings on the gauge. I did testing on the temp senders somewhere posted on DMCtalk.

The "O" switch and the thermostat MUST operate at the proper temperatures in order to work together. You can't go just by the temp gauge, they can be inaccurate. Another point to make about overheating, if you have a bad head gasket and combustion gasses are leaking into the coolant the car can overheat especially when under increased load like when you run the A/C. It can't hurt to do a combustion gas test on the cooling system. When you have done all of the "ordinary stuff" and you still have a problem it is time to look for the less common causes.

[Ron]

I would shoot the cylinder head next to the gauge sending unit and compare it to the gauge's reading.

Shooting the radiator's inlet and outlet can tell you a lot.
IIRC, 1669 showed a 22°F drop. (Most systems will show a 20-30°F drop.)

[rotproducciones]

Same here! My car gets hot when I turn AC (about 220), and stays cool when AC is not running, what I checked is that when I use the car with no AC on, the otterstat works perfectly, turning fans on and off when it's needed, but when I turn the AC on, the fans starts right away, and here is were the fans starts to act strange, after some minutes with AC on and of course fans running, the fans turns off and the temperature starts to rise and then nor the otterstat nor the AC are able to send a signal to the fans to turn them on again,,, is like both signals get in conflict and they can't get the fans to turn on again, so I need to turn off the AC and after a few minutes the otterstat takes control of the fans again, any comments on my theory about this "signals conflict" I'm imagining is happening on my car?

[Bitsyncmaster]

Same here! My car gets hot when I turn AC (about 220), and stays cool when AC is not running, what I checked is that when I use the car with no AC on, the otterstat works perfectly, turning fans on and off when it's needed, but when I turn the AC on, the fans starts right away, and here is were the fans starts to act strange, after some minutes with AC on and of course fans running, the fans turns off and the temperature starts to rise and then nor the otterstat nor the AC are able to send a signal to the fans to turn them on again,,, is like both signals get in conflict and they can't get the fans to turn on again, so I need to turn off the AC and after a few minutes the otterstat takes control of the fans again, any comments on my theory about this "signals conflict" I'm imagining is happening on my car?

Each signal drives a 12 volt signal through a diode to the fan relay control signal. So as long as the diodes are good there should be no way any coupling of those signals at the fan relay.

[DMC-Ron]

Same here! My car gets hot when I turn AC (about 220), and stays cool when AC is not running, what I checked is that when I use the car with no AC on, the otterstat works perfectly, turning fans on and off when it's needed, but when I turn the AC on, the fans starts right away, and here is were the fans starts to act strange, after some minutes with AC on and of course fans running, the fans turns off and the temperature starts to rise and then nor the otterstat nor the AC are able to send a signal to the fans to turn them on again,,, is like both signals get in conflict and they can't get the fans to turn on again, so I need to turn off the AC and after a few minutes the otterstat takes control of the fans again, any comments on my theory about this "signals conflict" I'm imagining is happening on my car?

Well, I'm wondering if your fans are drawing a lot of current (are they original)? When the AC is in operation, the fans are cycling with the compressor, and they spend a lot of time running. They may be pulling enough amperage to trip the thermal trip breaker when operating fairly continuously. Without the AC on the fans run a lot less (usually only when the car is not at speed) and the thermal trip gets a respite. Maybe the more continuous operation with AC is tripping the thermal breaker. This is when you notice the issue and you turn off the AC. Then the thermal resets coincidently with you turning things back on. Just a theory.

Ron

[David T]

If the fans are not cycling with the compressor, the circuit breaker is probably cycling them on and off. Upgrade the circuit breaker.

[Helirich]

Well, I'm wondering if your fans are drawing a lot of current (are they original)? When the AC is in operation, the fans are cycling with the compressor, and they spend a lot of time running. They may be pulling enough amperage to trip the thermal trip breaker when operating fairly continuously. Without the AC on the fans run a lot less (usually only when the car is not at speed) and the thermal trip gets a respite. Maybe the more continuous operation with AC is tripping the thermal breaker. This is when you notice the issue and you turn off the AC. Then the thermal resets coincidently with you turning things back on. Just a theory.

Ron

I don’t believe my fans cycle with the compressor. They just turn on with the AC switch. The compressor can cycle (or not), but the fans are on as long as the switch is on.

Edit, thinking more, maybe they just appear that way to me because they are on with the key when the car is not running. My compressor doesn’t cycle much.

[Ron]

Edit, thinking more, maybe they just appear that way to me because they are on with the key when the car is not running.Yep.
(As David reminded me...Power from the AC switch goes through the cycle switch first....)