[TaxiGirl]

Hello. I just stopped by dealer because i could not find a part number for the ac relay. Turns out there is no part number but, there is a spare relay in fuse box. If that one does not work then maybe the TPIM which i had replaced last July.
Does anyone have any idea how i determine the problem?
What is the low side psi and the higjside psi supposed to be?

 

[valiant67]

PSI will depend on ambient temperature.
With the A/C getting hot at idle and cool at speed, it's probably not the relay. I'd bet on either a refrigerant charge issue or the cooling fans not pulling enough air (though I'd suspect the engine would get warm at idle in that case).

 

[TaxiGirl]

PSI will depend on ambient temperature.
With the A/C getting hot at idle and cool at speed, it's probably not the relay. I'd bet on either a refrigerant charge issue or the cooling fans not pulling enough air (though I'd suspect the engine would get warm at idle in that case).

Hi. I noticed when he put gages on that the low side is around 50psi and high side was 150psi. It is hot as hell down here. Probably the ambient temp was 98 degrees

 

[TaxiGirl]

PSI will depend on ambient temperature.
With the A/C getting hot at idle and cool at speed, it's probably not the relay. I'd bet on either a refrigerant charge issue or the cooling fans not pulling enough air (though I'd suspect the engine would get warm at idle in that case).[/QUOTE

AT 98 degrees ambient, isnt the high side too low?

 

[TaxiGirl]

PSI will depend on ambient temperature.
With the A/C getting hot at idle and cool at speed, it's probably not the relay. I'd bet on either a refrigerant charge issue or the cooling fans not pulling enough air (though I'd suspect the engine would get warm at idle in that case).

Do you know what voltage is supplied to the relay from the TIPM when ac is supposed to be running?

 

[ImperialCrown]

This chart shows the expected pressures at given temperatures.
33aylu8.jpg
Relay voltage should roughly be battery (+) voltage with the engine running and A/C on.
If it is cooling OK while you are driving, but blowing warm when you are stopped at an idle, then it doesn't sound to me like a TIPM or relay problem.
Do the radiator electric fans come on and run when the A/C is on and the vehicle parked? If air isn't moving through the condenser in front of the radiator, then it won't blow cold air in the vehicle. Heat needs to be removed from the condenser by the fans running or air blowing through the grille at highway speeds.
While you are driving, plenty of air is blowing through the condenser and it is able to cool the interior.
If the electric fans are not running, then the hi-side pressure will skyrocket and you may have already lost some of the charge out the hi-pressure relief valve. You will need to add charge after the fans are fixed.
At 98°F, I would expect a hi-side pressure of 280-300 psi with the fans on according to the above chart.

 

[TaxiGirl]

This chart shows the expected pressures at given temperatures.
33aylu8.jpg
Relay voltage should roughly be battery (+) voltage with the engine running and A/C on.
If it is cooling OK while you are driving, but blowing warm when you are stopped at an idle, then it doesn't sound to me like a TIPM or relay problem.
Do the radiator electric fans come on and run when the A/C is on and the vehicle parked? If air isn't moving through the condenser in front of the radiator, then it won't blow cold air in the vehicle. Heat needs to be removed from the condenser by the fans running or air blowing through the grille at highway speeds.
While you are driving, plenty of air is blowing through the condenser and it is able to cool the interior.
If the electric fans are not running, then the hi-side pressure will skyrocket and you may have already lost some of the charge out the hi-pressure relief valve. You will need to add charge after the fans are fixed.
At 98°F, I would expect a hi-side pressure of 280-300 psi with the fans on according to the above chart.

HI, thank you. Yes fan is running when it is supposed to run.

Are there high and low psi switches?

 

[ImperialCrown]

There is a pressure transducer that tells the PCM the high-side pressure. The PCM uses this information to shut-down the A/C if the pressure is too high or too low. It will cycle the fans on or off depending on high-side pressure in normal operation.
An evaporator temperature sensor will tell the PCM the evap temp. It will use this information to cycle the compressor to keep the evap as cold as possible without danger of freezing. About 36°F.

 

[TaxiGirl]

There is a pressure transducer that tells the PCM the high-side pressure. The PCM uses this information to shut-down the A/C if the pressure is too high or too low. It will cycle the fans on or off depending on high-side pressure in normal operation.
An evaporator temperature sensor will tell the PCM the evap temp. It will use this information to cycle the compressor to keep the evap as cold as possible without danger of freezing. About 36°F.

Thank you for that, but are they accessible? Can i test them?

 

[ImperialCrown]

They are both easily watched with a good scan tool. The transducer pressure should closely match the hi-side gauge pressure.
The evap temp is best seen with a scan tool. If you can see the evaporator fins from under the dash, they should be wet with condensate, but not white with frost.
The transducer and sensor probe may or may not set a fault code.

 

[Bob Lincoln]

Hi. I noticed when he put gages on that the low side is around 50psi and high side was 150psi. It is hot as hell down here. Probably the ambient temp was 98 degrees

If this is accurate, it is almost certainly undercharged. As IC said, pressures should be quite a bit higher, at least 250-300 psi high at that ambient temperature.

 

[ka9yhd]

In the title to this post "blows cold when moving hot when idle" This almost sounds like an air flow issue. What is the condition of the condenser possibly clogged with dirt and other debris?

 

[TaxiGirl]

In the title to this post "blows cold when moving hot when idle" This almost sounds like an air flow issue. What is the condition of the condenser possibly clogged with dirt and other debris?

How would i know the condition of the condensor?

I am at a shop now and yesterday when i had it looked at the guy put in .38 lbs of freon and before i got out of the parking lot, it was blowing hot in the front and the rear a/c was still working. Today i went to a different mechanic shop and they said there was 2.83 lbs of freon and it was overcharged and they recovered that and i was charged $110. So, i am getting ready to leave and I notice that the rear ac is not coming on. So, now I am paying them $54 just to take the rear a/c panel off to check to see if power is getting to the blower. If power is not being supplied to the blower the only other thing i can think of is it is not being told to come on from the pcm. Or the switches in the front are not working. The sync light is coming on but nothing i do is turning on the rear a/c. Although the rear a/c worked yesterday.

WELL. There is no power being supplied to the rear a/c blower

 

[Jerry Simcik]

Hi. I noticed when he put gages on that the low side is around 50psi and high side was 150psi. It is hot as hell down here. Probably the ambient temp was 98 degrees

Again, as stated, this indicates an undercharged condition. HOWEVER, it could also indicate a lack of compression also. The operation of the clutch and compressor should be verified as well. (If the clutch cycles on and off frequently, there may be an issue. Also, if the compressor is worn, or there is a leak, the compressor may not be able to pressurize the refirgerant accordingly.)

If the system is full of freon and you're still getting these low gauge readings, the compressor or clutch are likely your issue (other issues, such as blockages, would cause noticeable spikes in one of the pressures.)

For your rear blower, make sure you have not accidentally turned it off or set it to the rear cabin controls on the main panel. The main panel can override the rear panel, which could cause someone to mistakenly assume that the rear panel is not working.

 

[TaxiGirl]

Again, as stated, this indicates an undercharged condition. HOWEVER, it could also indicate a lack of compression also. The operation of the clutch and compressor should be verified as well. (If the clutch cycles on and off frequently, there may be an issue. Also, if the compressor is worn, or there is a leak, the compressor may not be able to pressurize the refirgerant accordingly.)

If the system is full of freon and you're still getting these low gauge readings, the compressor or clutch are likely your issue (other issues, such as blockages, would cause noticeable spikes in one of the pressures.)

For your rear blower, make sure you have not accidentally turned it off or set it to the rear cabin controls on the main panel. The main panel can override the rear panel, which could cause someone to mistakenly assume that the rear panel is not working.

I have not turned it off. Is there a fuse for the rear blower? The sync light is on and there is no pwr being supplied to the rear blower

 

[Jerry Simcik]

It has been a while since I've actually played with the HVAC controls in a van...

I believe you can have the system synced while still having the rear A/C off (Sync should only sync the temp of the front two zones, unless you also have the rear set to front control and auto temp). You need to verify that you have the rear A/C control panel locked, so that it can only be controlled by the main (front) controller and you need to verify that the rear is not off. You should see "REAR AUTO" in the middle of the temperature display. (If you have a 2011, look at page 333 of your owner's manual and read from there.)

If you're unsure of this, simply poke your head in the back and turn the rear controls to their maximum cooling settings.

Once you have verified that the settings are correct on the controls, and the rear motor is still not working, we can look at the next step:

The next thing to check is to turn the rear fan speed to it's highest setting (use both sets of controls if you're uncertain of which one is actually controlling the system). If the fan suddenly starts working, but works only on the high setting, then the rear blower motor resistor has failed. If the fan does not work at all on any speed setting, this is not your issue.

If the controls are set correctly and the rear fan is not working, then the issue gets harder to diagnose. There is no fuse for the rear blower motor. You could have poor connection, a failed motor, a cut wire, a bad relay, a bad control unit, or some other gremlin, and will require tools such as a multimeter, at minimum, to go much further with. If you're handy with a wrench and have tools, we can go a bit further. If not, I'd suggest taking it to a dealer for diagnosis.

 

[TaxiGirl]

It has been a while since I've actually played with the HVAC controls in a van...

I believe you can have the system synced while still having the rear A/C off (Sync should only sync the temp of the front two zones, unless you also have the rear set to front control and auto temp). You need to verify that you have the rear A/C control panel locked, so that it can only be controlled by the main (front) controller and you need to verify that the rear is not off. You should see "REAR AUTO" in the middle of the temperature display. (If you have a 2011, look at page 333 of your owner's manual and read from there.)

If you're unsure of this, simply poke your head in the back and turn the rear controls to their maximum cooling settings.

Once you have verified that the settings are correct on the controls, and the rear motor is still not working, we can look at the next step:

The next thing to check is to turn the rear fan speed to it's highest setting (use both sets of controls if you're uncertain of which one is actually controlling the system). If the fan suddenly starts working, but works only on the high setting, then the rear blower motor resistor has failed. If the fan does not work at all on any speed setting, this is not your issue.

If the controls are set correctly and the rear fan is not working, then the issue gets harder to diagnose. There is no fuse for the rear blower motor. You could have poor connection, a failed motor, a cut wire, a bad relay, a bad control unit, or some other gremlin, and will require tools such as a multimeter, at minimum, to go much further with. If you're handy with a wrench and have tools, we can go a bit further. If not, I'd suggest taking it to a dealer for diagnosis.

Thank You Jerry. I have been trying to respond to your post but, Microsoft has almost rendered my laptop useless, like they have with everyone that I have ever have had before.
The blower motor was not getting the power with the settings set correctly and since it feels like it is 150 degrees outside, I just took it to the dealer. I have a bad feeling about the whole thing because the day that I took it to the dealer I had some other unexplained surges in the power and at one point the temps on my radiator and oil surged to 235 degrees. I stopped got out and everything seemed to be fine. I also noticed that my less than a year old Sears Diehard battery seemed to be bulging little at the top. These are signs to me that the TIPM IS GOING OUT AGAIN.

 

[Doug D]

If the battery is bulging I would have it checked ASAP. That is NOT a good sign. The battery is being overcharged. The swelling is the build up of hydrogen gas and it could very well explode. Personally, I would not drive it until a proper diagnosis is completed.

Sounds like a good diagnostic check needs to be performed. I'm not discounting the TIPM being bad, but I would want to rule out all other possibilities before replacing the TIPM. They are very pricey.

 

[Doug D]

It could also swell from excessive heat, but I would definitely have the charging system checked. More than likely the voltage regulator (which is in the TIPM?) is faulty. Again - it could be the excessive heat causing it to not regulate properly. Either way it should be checked.

 

[ImperialCrown]

Underhood heat during taxi-duty can get pretty high with prolonged idling and A/C use.
The factory battery is wrapped with a Thermoguard® cover.
Many times after a battery replacement, this cover is forgotten and not reinstalled. It is more important than it looks. Make sure that it is in place.
Dodge Grand Caravan C/V. #05235267AD: COVER. Battery. Thermoguard.