Dash AC Problem

ernie1 wrote:
Not saying this has anything to do with your primary concern of the compressor not shutting off but is in regards to your statement of the air compressor sound from your ac compressor. You really should have a set of ac gauges hooked up to your ac system. This will tell you many things that is or is not wrong with the system and/or what is causing the noise you mentioned like maybe excessive high head pressure, something internal like a rod clanging etc. You mentioned that the noise occurs after the system is run awhile so I was thinking increasing head pressure. Has the unit been worked on recently and maybe the refrigerant charge has been contaminated with air and moisture which will cause very high head pressures?

We were on our way from Alabama to Florida last week when the serpentine belt broke. I replaced the belt, but upon starting the engine found out the compressor was locked up and new belt was just slipping over the AC pulley. So we were towed to a repair shop where they replaced the compressor, drier, etc. they evacuated and backflushed the system.
All appeared well until we stopped a few hours later. It was not warm enough for Ac or cool enough for heat, so switch was off. When I went to check the oil I noticed ice on the AC lines. I called the shop and he told me to disconnect the connection of the low pressure switch on top of the dryer. I did that, but found out that the Ac was engaged all the time anyway. So when we got to Zephyrhills, I started this thread to see if I could figure this out.

j-d wrote:
Doggone! Relay was supposed to solve ALL the problems! You can see from the few pins it has and the diagram on it, that all it's able to do is be ON or OFF when told to. Other odd behavior is coming from somewhere else.

Couple more questions:

Did the Compressor run in all selections before?

Are your A/C controls Manual or Electronic?

Does that Manual linked in this thread match your Coach?

Did the sound of the compressor change from before changing the relay to after changing it?

Do you know if your system is meant to cycle? Many modern ones do not.

Answers:

Yes, ran in all selections, including "off"

AC controls are manual (knob selector)

The manual in the link is correct

Yes, the compressor never made the puffing sound before.

Not sure if it should cycle; just assumed it should

Not saying this has anything to do with your primary concern of the compressor not shutting off but is in regards to your statement of the air compressor sound from your ac compressor. You really should have a set of ac gauges hooked up to your ac system. This will tell you many things that is or is not wrong with the system and/or what is causing the noise you mentioned like maybe excessive high head pressure, something internal like a rod clanging etc. You mentioned that the noise occurs after the system is run awhile so I was thinking increasing head pressure. Has the unit been worked on recently and maybe the refrigerant charge has been contaminated with air and moisture which will cause very high head pressures?

You ask Which switch:
YOu said in your original post: My dash AC stays on regardless of the switch setting

That switch, You have the blower speed control, then the temp control, then the MODE switch.. That is the switch, the MODE switch.

To test: Find the relay someone else pointed you to and measure the voltage on teh two coil contats,, present - either bad switch or short in wires, Absent - bad relay.

Doggone! Relay was supposed to solve ALL the problems! You can see from the few pins it has and the diagram on it, that all it's able to do is be ON or OFF when told to. Other odd behavior is coming from somewhere else.

Couple more questions:

Did the Compressor run in all selections before?

Are your A/C controls Manual or Electronic?

Does that Manual linked in this thread match your Coach?

Did the sound of the compressor change from before changing the relay to after changing it?

Do you know if your system is meant to cycle? Many modern ones do not.

Update: Replaced relay. The only difference is that it now disengages when turned to "off". It engages on "all" the other switch selections. I let it run quite a while and there was no cycling. Also after it ran a while, the compressor sounded like an air compessor! It had that puffing sort of sound.
Please chime in with answers or??????

YESSIR! If 30 and 87 have continuity with the Relay OUT of the coach, then you have what Matt suspected above, Stuck Relay. Continuity 85-86 means the Coil is still good. Contacts probably fused as Matt noted. You might be able to rap it on a hard surface and get 87 to release, but it'll stick again. There's probably a plating of "noble" metal on the contact points that has worn away.

Hint: Radio Shack used to carry these relays, in store stock. They used to have the 87A terminal. If your socket doesn't have a hole to allow 87A to plug in, just take the pliers on your Leatherman Tool and worry that one off. Just be sure it isn't 87-no-A. They went to a mounting tab on the top, you can cut that off too.

On Amazon, you can get FIVE with sockets for $14 or one for $3-something. Many choices if you search "12vdc relay" and some are Prime.

Here the Little Sucker is at RatShak! No 87A terminal. Just cut the plastic tab off if the cover won't go back onto your panel.



You can tell from the diagram on its face there's no 87A.

Radio Shack Model: 275-001 or Catalog #: 2750001 $6.49

j-d wrote:
This Link is "A" Workhorse Manual. Maybe matches yours, maybe not. I found the A/C Compressor Relay in the "outside" fuse box and it's pictured as a square relay, looking at it from the top. Is this thing a Cube. around an inch on a side? If it is, could well be a "Bosch Relay" and here's the wiring diagram for it. If yours has five terminals, there should be continuity between 30 and 87A with the relay out of the vehicle. Out of vehicle, between 30 and 87 should be OPEN. 85 and 86 are the coil that pulls the relay into contact, so there should be continuity across them. If you have test leads, you can put 12VDC to 86 and ground to 85. Relay should click and then 30 and 87 would have continuity. 30 and 87A would now be OPEN. Not every Bosch has five terminals. If it doesn't then just disregard what I said about 87A.

Thanks. Same looking relay except there is no 87a. There "is" continuity between 30 and 87. 85 and 86 have continuity. So bad relay?

ernie1 wrote:
Could it be because you have the heater set on the defrost mode?

No. Runs even when off.

wa8yxm wrote:
Two things .. The switch and optionally a relay.

What switch?