AC and heat not working. Any Ideas as to why?

[BigKO]

OK guys, I have a couple issues with my car that need to be resolved. (as most do).
These are mostly accessories on the car that I just want to get working. Be prepared most of them aren't working LOL. BUT I am just looking for places to start when I get ready to tackle them all.

1st! The AC and heat are not working. The blower (fans) push the air, but it neither heats up or cools down. Its just ambient temperature. As far as I know, everything is hooked up (heater hoses, AC hoses, etc.)

What I've done so far: Went to get the freon filled up, it was needed but it still didn't work. The AC place then determined that the compressor never turns on (voltage doesn't get to the plug). Haven't double checked there work yet, and was wondering what relay or sensor would most likely cause this? or if I should look elsewhere. Could this be caused by a bad Climate control unit (some of the lights don't work, and buttons don't work either sometimes) I have another I can try but thought this least likely.

This is mostly just brainstorming at this point, and any ideas or past experiences with issues like this would help. Thanks!

 

[whitemike]

What motor?

 

[BigKO]

7mgte, sorry forgot to list that. Also R154 as that also changes the AC system quite abit

---------- Post added at 03:13 PM ---------- Previous post was at 03:04 PM ----------

Hmm well I was looking at the troubleshooter on the TSRM and I'm thinking it could be the pressure switches located by the passenger side wheel well (inside the engine bay). Would those cause that with the AC though?

http://www.cygnusx1.net/Supra/Library/TSRM/MK3/manual.aspx?Section=AC&P=15 (I suppose this provides a good place to start ) haha. But has anyone ever experienced this issue before?

 

[Satan]

Maybe the CIG fuse... I think There is a fuse you should check for, which seems unrelated (sorry, can't remember which). Look at the a/C troubleshooting guide and/or A/C wiring/circuit area in the TRSM.

 

[BigKO]

Maybe the CIG fuse... I think There is a fuse you should check for, which seems unrelated (sorry, can't remember which). Look at the a/C troubleshooting guide and/or A/C wiring/circuit area in the TRSM.

Hmm any luck remembering that random fuse?
No tips as to things to start checking? I kind of just want to generate a most likely list. Im sure I just need to put the time in. Any ideas what would cause the heat not to work at all?

 

[Figit090]

I have been told that problems with the heater not working can be caused by the climate control unit going bad. First it can get erratic (you might have to crank it to 85 to get any real heat, and then it blazes), but I think it can also fail you completely and not give any heat. I sometimes have to put it to 75-80 to get warm air, when I remember it being more accurate and responsive before. Then i was told about the issues and just live with it (until it dies completely that is).

Look into that, I'd say it's actually a likely possibility that your CC unit is just not telling the rest of the system to give you heat. That's coming from someone unsure about how the system works, but it seems probable that the compressor wouldn't kick on either if the main control unit isn't saying it needs too. I don't know what lack of voltage at the plug tells you.

Hope that helps, do some searching on the climate control, see what you come up with. I might be able to find the thread where I was inquiring about my issues.

 

[Satan]

Page AC-4 of the TRSM shows the CIG and GAUGE fuses in the A/C system circuit. GAUGE is a 7.5A in the # 1 spot and CIG is at #4 (Driver's side kick panel).

 

[BigKO]

To Figit: Thanks! I'm thinking that same thing. I like you also have very limited knowledge of the AC system. LOL But I figured if the climate control were to fail internally (Buttons not pushing in correctly, half the lights not working) that it would be a likely source of the problem.

To Satan: I checked all of the fuses before visually, and replaed the AC one for good measure. I will double check those and read up more in the TSRM.

Side Note: Anyone think its worth changing out the climate control to a unit I know the heat works in? (AC didnt work because it needed a recharge on the previous car).
Second, Anyone have any idea how those pressure switches (not sure of the accurate name) work? How do I check them? And what is there purpose?

Thanks for all the help

 

[GrimJack]

There is a good chance that the AC and the heat are two separate issues.

For the heat, check that the heater control valve is actually working. It's in the engine bay on the passenger side of the firewall - the big vacuum actuated valve that connects to coolant lines from the back of the head. These are commonly bad in two ways.
1. The electrical solenoid on them goes bad, and vacuum is no longer sent to the valve. Check this by running a vacuum line straight to the valve.
2. The vacuum actuator goes bad, and even with vacuum it no longer moves. Check this by manually pushing the valve open while a buddy checks for heat inside.

For the AC, find a magician ... err, I mean, AC technician. IMO, hot humid air goes in, magic happens, cold, arid air comes out. If anything goes wrong in the middle, I need a magician.

 

[BigKO]

There is a good chance that the AC and the heat are two separate issues.

For the heat, check that the heater control valve is actually working. It's in the engine bay on the passenger side of the firewall - the big vacuum actuated valve that connects to coolant lines from the back of the head. These are commonly bad in two ways.
1. The electrical solenoid on them goes bad, and vacuum is no longer sent to the valve. Check this by running a vacuum line straight to the valve.
2. The vacuum actuator goes bad, and even with vacuum it no longer moves. Check this by manually pushing the valve open while a buddy checks for heat inside.

For the AC, find a magician ... err, I mean, AC technician. IMO, hot humid air goes in, magic happens, cold, arid air comes out. If anything goes wrong in the middle, I need a magician.

LOL on AC! I feel the same way. Only problem is that I took it to an AC "technician" who apparently said I only repair the mechanical aspects. This was when I got the AC recharged. He basically told me that it wasn't working because of electrical problems, and that power wasn't getting to the compressor. So basically he had no idea what the hell was going on either LOL.
Thanks for the tips on the heater valve. I was curious if that may be the problem. I have the other one from the car I am parting out still. I will check it and then replace if necessary when I get back from my Vacation lol.

 

[GrimJack]

I think you should find a better magician.

 

[BigKO]

Agreed, its not an exclusive AC shop, they are mostly just a tire wheel and basic suspension place, just went there because they had a good deal on the AC recharge. Did a lot of investigating for what I paid so I'm not too worried about it. They do a good job in their areas of focus, and are honest hard working people. HAHA but definitely not magicians!

 

[hvyman]

there are 6 fuses for the a/c system. I would first check all your fuses to make sure none of them are blown.

 

[Nick M]

Hmm well I was looking at the troubleshooter on the TSRM and I'm thinking it could be the pressure switches located by the passenger side wheel well (inside the engine bay). Would those cause that with the AC though?

The dual pressure switch is a high and low switch. They are in series, and the compressor will not run without both sides closing.

 

[BigKO]

I believe that is my problem, because when my (magician) did some testing, he stated that power was getting to one side of the pressure switches, but nothing was coming out of them, so probably one or both have failed for some unknown reason. I think I am just going to start by replacing those. Are they easy to replace like just plug or screw in? I have those as well.

And in regard to the fuses, I checked all of the fuses in the kick panel and passenger panel, and under the hood when addressing a different problem. I then found out that the problem was relay related. This was only a visual check however.

 

[Nick M]

The A/C amplifier supplies ground to the clutch relay when the dual switches are closed. And the dual pressure switch is in series with power to the other side (switched) of the clutch relay.

http://www.cygnusx1.net/Supra/Library/TSRM/MK3/manual.aspx?S=AC&P=32

 

[BigKO]

Thanks thats a big help. I'll ge right on that. I definitely need the AC where I live. LOL gotta make sure my girl and I can ride in the car comfortably

 

[BigKO]

I though I would go ahead and update this thread....

Well, I got the heat working (faulty heater valve). Just replaced it with a working one from my parts car. (thanks grim jack). I then also saw that no matter what the temperature on the control unit, that the heater valve was at full open (full heat). According to the page below, and the following page from the TSRM. This signals that I have an open circuit somewhere.

http://cygnusx1.net/Supra/Library/TSRM/MK3/manual.aspx?S=AC&P=40 (page 40)
http://cygnusx1.net/Supra/Library/TSRM/MK3/manual.aspx?S=AC&P=41 (page 41)


on page 41, it states that from condition A on page 40 (open circuit) that the heater valve would remain full open. However I am not sure If I am understanding this diagram correctly. I believe this is referring to an open circuit in the Amplifier ??(inside the control unit). Or is it referring to the entire system?

Any help is appreciated.

An additional tip (possibly related, possibly not) is my two smaller auxiliary fans never come on. (during testing at the AC place, when they were testing voltage on the pressure switches they came on) Is this possibly related?

 

[GrimJack]

The heater valve will only close if you have the climate control set to FULL cold. Usual things to check are the vacuum line supplying it, and the VSV that switches the vacuum.

The two smaller aux fans only come on for me when the car is actually overheating... I've never seen them run except when I had a BHG.

 

[BigKO]

Yes even at full cold it does not close. Vacuum lines are good no cracks etc. Did you look at the diagrams I linked to? Sound likely? Could be the source of full open at all times, and non functioning AC.