Cooling issues w/ the AC on

[9FASTANG5]

I have spent the last few evenings reading over posts I’ve found while searching Corral.net, but did not really find what I was looking for, so here goes.

My 95GT has a cooling issue when the AC is activated in somewhat stop n’ go traffic. The stock temp gauge quickly climbs to the L in normal and stays put. Once the AC is turned off, it eventually goes back to normal.
Last week, I replaced the water pump and that has obviously not fixed the problem. I am going to replace the two sensors (the sending unit and the temp sensor) and see what happens. I am also going to check for corrosion / melting at the fan relay.

Can you guys help me pinpoint this before I spend money I don’t really have chasing this down?
• Would recharging an 11 year old AC system make this problem go away? It still blows cold, so I have no AC line leaks; but could the pressure be down enough to make it have to work harder, thus raising the temp? If I’m driving it, the top is down; but my wife likes her AC, so it still needed.
• I will clean the AC condenser and radiator fins at the carwash to remove any debris caught in the fins.
• I have the stock radiator, so that could be replaced; but that will be last on the list.

Anything else you suspect might be causing this, post it up and I’ll check it out.


Thanks,

[r3dn3ck]

flush the cooling system really well and get a new thermostat if yours is more than a couple years old. Other than that it looks like you're dead on for how I'd troubleshoot it.

If you're going to recharge, I'd look at a R134a conversion if you're car uses R12 stock. The R12 Freon is 100bucks a pound, 134a is MUCH cheaper.

[9FASTANG5]

Originally Posted by r3dn3ck

flush the cooling system really well and get a new thermostat if yours is more than a couple years old. Other than that it looks like you're dead on for how I'd troubleshoot it..

I was planning on it and the T-stat is two years old, but I'm gonna replace it anyway.

Originally Posted by r3dn3ck

If you're going to recharge, I'd look at a R134a conversion if you're car uses R12 stock. The R12 Freon is 100bucks a pound, 134a is MUCH cheaper.

Does anyone know when they switched to 134A?

[r3dn3ck]

there should be a little yellow tag somewhere on the system that tells you what refrigerant it takes.

other than that... IIRC I was pretty young when the change to 134a was made (I remember protesting the change by exploding a case of R12 cans with automatic weapons fire in my back yard). I'm pretty sure it was pre-92 but someone else will have to be the expert on that.

[9FASTANG5]

I just came back from driving for about 20 minutes on the freeway w/ the AC on Max and the temp guage never went past the R in normal. So the problem is definately at stop n' go speeds. Does this narrow it down any further?

[9FASTANG5]

Originally Posted by r3dn3ck

(I remember protesting the change by exploding a case of R12 cans with automatic weapons fire in my back yard).

Nice work!

[Chopper]

Originally Posted by 9FASTANG5

I just came back from driving for about 20 minutes on the freeway w/ the AC on Max and the temp guage never went past the R in normal. So the problem is definately at stop n' go speeds. Does this narrow it down any further?

Yes it narrows the fault to an airflow disruption.Drive the car untill it's warmed up and bring it home and leave it running with the A/C off.The low speed circuit will turn the fan "on" when the coolant temp. reaches 221* then it will turn the fan "off" when the coolant reaches 200*.The high speed portion of the circuit only operates when the engine is hot AND the A/C is on.
If the fan isn't running at low and high speed then the problem is in the connections or the CCRM (Constant Control Relay Module) itself.
The temperature sensors can be tested by disconnecting the electrical connector at the sender and connecting an ohmmeter between the senders terminal and an engine ground.When the engine is cold the senders resistance should be around 74 ohms.As the engine warms up the resistance should drop and at full operating temp. should be around 9.7 ohms.The 4.6 engine has two temperature sensors.The one on the drivers side is the one going to the computer and the one on the passenger side is for the guage.
Keep us posted on your progress.

[jareds98gt]

is the fan coming on while your sitting in traffic? if not fix that first before you start throwing money at it, hoping your going to fix it.

[9FASTANG5]

Yes, the fan is coming on - hi and lo speed work fine.
Today, I changed the thermostat, harmonic balancer (Just cause I had everthing up front removed already and it was staring to wobble), removed the radiator and went to the local car wash and pressure washed the radiator from the back forward to remove all the stuff that was jammed in there. After re-assembling it all, I had to take a break; it's 95* and humid, so I have not driven it since this was all performed, but I keep eveyone in the loop as to my progress.