A/C and Heater don't turn on sometimes

[z258_14]

Hi All,

I posted about this problem about a year ago, so far I have brought the car to the toyota service centers three times but they couldn't fix it. I want to try (again) to fix it myself.

I have a 2003 Toyota Corolla (Canadian edition). Sometimes when I try to turn on the A/C nothing happens, the A/C light remains off, and no air comes out, similarly, even when the A/C button is off, and I just want to turn on the fan, it does not start at all (which means that the power doesn't reach to the blower motor). Usually, when I try to turn on/off a couple of times it starts to work, but sometimes it takes a while to turn on (specially on hot days that we need the A/C most). I had the same issue in winter as well, when I wanted to turn on the heater, it didn't turn on (sometimes), but after some playing with it, it would turn on eventually (but again sometimes it didn't on very cold days).

Using the electrical diagrams of the Air Conditioner below



As far as I have checked, when I turn on the A/C no matter if it is actually turned on or not, I can sense a click from the HTR relay (located above dashboard/glove box). But on the times that the A/C doesn't turn on, there is no voltage on the actuator pins of M/G CLT Relay (from the engine room relay box), which means that whatever the problem is, it happens before that.

The HTR Relay is in the RH R/B (pictured below) which is not very accessible



I noticed a few things when I touch the relays:

1. The HTR Relay itself clicks when I turn on the A/C no matter what, also I didn't notice any change of temprature in it.
2. The P-POINT Relay became very warm (which was unusual for me, maybe it was due to constantly playing with the A/C. In any case apart from the A/C problem I haven't noticed any other issue with my car and aparently P-POINT relay is not related to A/C.
3. There isn't any TAIL Relay or INV Relay there, I can touch the empty plugs with my fingers but there is no relay. Is this normal ?

Any comments are highly appreciated.

Thanks a lot in advance,

[karazy]

It seems like the problem is with the blower sw/ or the IG ground. Remember that the AC won't work unless the blower has power and the heater relay (pins 1 & 2) is energized by the blower sw/ as well. I would hope it is just a bad ground and check all the junctions in this line first. Then I would check the blower sw/. The chances of it being the blower or the resistor bank are slim, but not impossible. The trouble with intermittent snags is that they like to work properly when tested.

Good luck.

[dorman68]

I would try the ac/compressor clutch relay. The local dealer around here always has about 4 or 5 in stock, the parts guy stated that they are very prone to failure.

[karazy]

Originally Posted by dorman68

I would try the ac/compressor clutch relay. The local dealer around here always has about 4 or 5 in stock, the parts guy stated that they are very prone to failure.

If it was just an AC problem, but the fan itself is intermittent.

[z258_14]

karazy and dorman68,

Thanks a lot for the comments.

dorman68: Upon seeing that there was a TSB suggesting that the original MG CLT Relay should be replaced with a newer part, I suspected the same (I found a lot of posts in the net saying that their AC light was blinking (which happens sometimes to me too) and it was due to that part). But as I mentioned on my first post, I checked the voltage around pins 1 and 2 on that relay, and in the cases that the AC didn't work, there was no voltage (there is a voltage there when the AC works). This means that even if that part might have issues, my current problems are not coming from there. Am I right in my reasoning ?

karazy: If you check pin 1 of the HTR Relay, it goes directly to the Blower SW, I said in my first post that whenever I try to turn on the AC/Heater, I can clearly sense (and hear) that the HTR relay clicks, this means that the connection between relay and Blower SW, and also the connection between Blower SW and Ground is good. Also if you check pin 3 of the HTR Relay, if goes to the Blower motor itself and then goes to the Blower Resistor. Also the same pin goes to AC Switch Light as well as the MG CLT Relay. If I had a problem in Blower Resistor (or the Blower Motor itself), both the AC Light and MG CLT Relay should have worked, no matter if the AC works or not, which is not the case in my car. Am I right ?

I am suspecting on the HTR Relay itself. Unfortunately, it is located in a hard to reach position, and I can't test it using multimeter. The problem is that the OEM part is more than 100$ and I don't want to pay any more money to the stupid toyota technicians (using their resources it was very easy to pin-point the problem, which they couldn't). I have already ordered a used part from eBay (just to check).

Any other comments ?

Thanks a lot in advance,

[z258_14]

I also want to add a few more questions:

1. When I took out the HTR Relay, there was something greasy on its pins (white), I thought maybe it was to prevent corrosion or something. There wasn't anything on the relay next to it (P-POINT Relay). Is this normal ?

2. Any idea why the P-Point Relay became warm ?

3. Any idea why I don't have TAIL Relay and INV Relay ? Is this the case for other corollas ?

Thanks again for your comments,

[karazy]

When you say the relay clicks, does the fan actually operate? This relay has two positions. The solenoid in the relay will only get energized with the fan on. Pin 4 grounds pin 3 when the fan is off.

The p-point relay is on when the ign is turned to acc or on. Its for the rear power socket.

The tail relay is only on US cars and I'm guessing you don't have an inverter installed, thus no relay.

Do you know what the stealers did/tried?

[z258_14]

HTR Relay clicks "every time" that I (try to) turn on the AC by rotating the Blower SW. Sometimes AC/Heater/Blower works and sometimes doesn't (regardless of the clicks which happen all the time).

Well, on the first time I brought the car to Canadian Tire, after charging 50$ and working on it for about half an hour, they told me they can't do anything and I have to go to Toyota Service Center.

The second time, I went to the Toyota Service. I was able to show them the symptoms (and the AC didn't actually work there), the technician started by opening the front panel (the place where all the AC buttons, radio, ... are). Then the AC started to work and he couldn't go further. After charging me 80$, they told me that maybe one of the connectors was loose.

The third time, I went to he same Toyota Service Center and told them that the problem still exists. They charged me 40$ just to tell me that they need to change the whole AC sub-system which is around 700$ ! I will never set my foot in that service center again.

[karazy]

Did you get the new relay?

[z258_14]

Hi karazy,

I got the relay but haven't installed it yet as I guess I have already found the cause of the problem.

In my earlier posts, I mentioned about a greasy white substance on the HTR relay contacts. At first I thought maybe it was there to prevent corrosion or ensuring good contact, but I guess I was wrong. Neither the relay besides HTR (P-Point Relay) nor any other relays that I checked had that substance on their contacts. I also sensed a pattern that whenever I took out that HTR relay and put it back, it worked for a while before becoming intermittent. After cleaning the contacts, it worked flawlessly for a week before stopping, I took it out and there was that grease all over the contacts again (but a little less than the first time), I cleaned the contacts again and it has been working for about two weeks till now.

It's a bit strange, as the place that I plug the relays seems clean (I can't see it, I can only touch it). So the grease must be inside and near the plugs of that relay box. I have no idea where it is coming from, maybe it was there since the car was assembled in 2003.

The AC seems to be working flawlessly now, and I am busy with other things, so I have decided not to touch it untill it stops operating again.

But anyone has any idea where that grease is coming from ? Is it possible that it is coming from the airbag compartment or something similar in that area ?

Thanks a lot in advance,