Baystate Jeepers

Can anyone help me work through this?

The a/c clutch engages and cycles normally during the two low fan speeds but not on either of the two high speeds. When it’s working the line into the evaporator gets icy cold and the air is cold as well, so it doesn't seem like a refrigerant problem. Blower motor works normally at all speeds.

What should I try next?

What happens or doesn't happen at the higher fan speeds? Compressor not cycle at all?

At high speed the compressor doesn't cycle. Does cycle at low speeds.

I guess it might be the speed switch since the blower resister is bypassed at high speed if I understand it correctly.

Have you tried all this while sitting still or moving. My AC vent has a vacuum leak somewhere and under acceleration feels like no AC because the AC is coming out of defrosters. You might be experiancing a similar issue.

I first noticed the issue while driving but then figured out the a/c wouldn't engage while standing/idling under high fan. The a/c works fine under low fan while driving or standing.

Went to Autozone but their replacement blower switch doesn't have the correct knob arm on it

Thats a weird problem. Id check to see if there is a loss of voltage at the comp when switched to the higher speeds. That would start to indicate the switch and or relays. The working while driving and not at a stop ????? Blows me away. Id push in the clutch and rev it up . FjR68

del_TJ wrote:At high speed the compressor doesn't cycle. Does cycle at low speeds.

I guess it might be the speed switch since the blower resister is bypassed at high speed if I understand it correctly.

I had a similar problem years ago in my saturn. Turns out it was the resistor pack/board. My low speed fan did not work the 2 higher speeds did. on low the AC indicator illuminatedbut not on high, compressor would cycle on/off on low but not on high. Swapped out the Bd and all was fine:-)

Update. To clarify, a/c cycles with fan on low driving or standing, a/c clutch doesn’t engage with fan on high while driving or standing.

Bought a Mopar 99-04 3 speed switch and it fixes the problem. BUT, speeds are Low-Med-High-OFF (not a 4 speed switch). I’d have to get creative with a dremel to make the switch work. Old on left, new on right. The shaft is too long. No smartas$ jokes please

No one make a 97-98 4 speed switch. The original speeds are Low-Med1-Med2-High. The only option is to buy the whole HVAC control face unit with a new switch for around $100. New Mopar 99-04 switch was $25.


What would you do?

Any chance someone like Collins Bros or one of the other secondhand Jeep parts dealers (like Second Life Jeep) many have them?

I think if the high setting on the new switch put out the same velocity as the high setting on the old switch, I would learn to live with the 3 speed switch. If it put out less, I'd be tempted to find the 4 speed.

Usually the control board controls the max fan output by letting the compressor cycle on AC , with any fan speed . MAX-Air locks the compressor and delivers one more speed to the blower not switched. 3 speed / 4 speed , might not make any difference in blower total speed , just how big the jumps are from one to high . See if your friends know anyone in HVAC . They may have a flow meter you could borrow. We used it to balance central air complaints of this room is colder or this room wont cool as well. The clarification statement would have me looking at the switch also. What about getting the switch out of a bone yard. FjR68