Thread: Intermittent A/C

On and off since last year. what would you do? Does freon just get low?

If freon was low then it would not work very well. It might get colder if it was not so hot outside but thats about it. If its on-off then it could be a wiring issue or the compressor is not engaging.

I just checked the wiring, all good. Relay seems OK. My foglight relay was completely burned out last year and I swapped harnesses and plug. The A/C relay is brown outside, so it is possible the relay is bad? Just covering the basics b4 digging into the compressor.

Low freon could cause cycling. There is a low pressure switch that monitors pressure, and if the freon is low, it would turn off when the pressure is low, and while the compressor is off the pressure builds back up, thus turning back on!

Hey Ian,
While under the hood, look at all of the AC line connection points for any oil or oily dirt. The rubber O-rings wears out and produces a slow freon leak leaving oily tell-tale signs at the connection points (also will show with a UV light and amber glasses).

I had the same symptoms as you last year, so I ook the car to a local shop and they tested my R12 pressure. It was low. My rubber O-ring seals were leaking along the lines and at connection points. I had the system evacuated, changed all of the O-rings (R12 O-rings are different than R134; get the right ones), and replaced AC Receiver-Dryer Accumulator. Then, he refilled the system using the evacuated freon and 1 can of R12. The parts were all ordered from Rock for about $35, the can of R12 was $60 and the labor was $150; totaling about $250.

Then the air was sooo cold, that I had frost coming from the vents. Some forum members told me that this was normal, so last summer I actually had the car icy cold during the hot humid days of August.

This year, guess what? Same freaking problem, intermittant AC. Well, this time its leaking from the seals on the expansion valve behind the dash.. So yesterday, I ordered additional seals and a new expansion valve
for around $50. Then, I will repay to have the system purged, install new stuff, refill, and top off with another can of R12 !!

Last summer, that was NOT frost. I was breathing R12 Freon in the car ! ! You have a young kid.. Dont risk breathing leaking freon.. Have it checked Ian...

Scotty, the O rings are about 2 years old. Definately no oil. 1st thing I checked. Tapping the relay seems to turn the compressor on. I am going to recheck the harness tomorrow and change relays.

Test the AC relay. I use a simple radio 9volt battery to quickly test relays.

ALL Relays with 6 terminals
/---[[]]---\
.( 2 || 1 )
. .( 7 5 )
. .( 6 3 )
. \-------/

1. Connect the DVM between terminals 3 & 5
2. Using 12v direct current (or a simple 9volt square battery):
. . Apply current between terminals 1 & 2 (coil)
3. You should hear a click and DVM should show continuity.
4. Now move the DVM to terminals 6 & 7, should also show continuity

ALL Relays with 4 terminals
/---[[]]---\
.( 1 || 2 )
. . (5.3)
.\--------/

1. Connect the DVM between terminals 3 & 5
2. Using 12v direct current (or a simple 9-volt battery):
Apply current between terminals 1 & 2 (coil)
3. You should hear a click and DVM should show continuity.

If you have a click when applying current to the coil (1 & 2) and continuity on the other pairs, your relay is good.

Ok, my daughter broke my DVM (I am buying one today) so I just rewired a new plug and a relay. It was great yesturday, but this morning it was the same. Had to tap the relay 2 times. What is tapping the relay doing?

OK, the 9V battery thing works. I have clicking between 1 and 2. I have to check between 3 and 5 when I get a DVM.
Oh. BTW, there is no 6 and 7. Just 1,2 ,3 and 5.

Sorry Ian, Ive been in meetings all day.
I thought the AC relay had 6 plugs. But the 3 and 5 is used to check for continuity with your DVM...

But if you get the click, we know that the relay coil is good.

Where is your AC relay where u can tap it? Mine is under the hood beside the battery with the fuel pump & fog lamp relay...

Tapping the relay does nothing but this could be a loose wire, shorted wire, cut wire, or connection push-out (the male connector is pushing out the female connection when you plug in the relay) or bad relay.. If its a 4 plug relay, just swap it for any other 4 plug relay temporary to test if your relay is bad... Most the 4 prong relays are the same (different colors for specific circuits but the same inside).

Then, really checkout the wiring harness going to the connectors. Look for breaks, cuts, or burned wire. See if you can force the AC to fluctuate by moving the wires. This will isolate the possible wire with problems.

LMK when you get another DVM.. I have some wiring test that you can run...
I will be a Jensen shop tomorrow (jen36). Send him a PM tomorrow to reach me...

Did all that this afternoon. I even rewired. I got a complete relay box when my fog light relay burned out. I cut and spliced in a new plug just in case, and have used 3 different relays. It would work real nice until I shut off the car. Then I could have to lift the hood, open the box and tap on the relay about 3 times to get the compressor to kick in.
It is just more fustrating because my time is limited these days and car is not a priority. Just a minor necessity and I need A/C.