My 91 Dodge B250 van 5.2L ac isn't blowing cold air due to compressor clutch not engaging. Check engine code 33 indicates a/c clutch relay circuit issue. The relay is functioning but I am only getting about 5 volts coming from the battery/alternator thru to the compressor.

My question first is how many volts is supposed to go to the compressor clutch coil to engage it?

Second, if it should be approx 12 volts and I only have 5, could the issue be the fusible link that feeds the relay?

Or what are the other possibilities that I don't know about which are probably many?
Thanks in advance for any help.

 

The first thing to check on a system that old is the amount of refrigerant. It's 30 years old and your charge may have leaked off. Has it been converted to R-134 or is it still R-12. The old R-12 has screw on connectors. The newer R-134 uses quick connect couplers. They are also different from each other. Now, it's possible you have an electrical issue. Check the simple things first. A parts store employee can tell by looking at the fittings if yours has been converted. If it has been converted, you can get a recharge kit and charge it up. I'd also put a shot of dye in it. You can get a UV test kit with a black light pen light and safety glasses that you MUST use. This will show if you have a leak and where it is.

You first need to know what refrigerant you have. That's where the parts store comes in. Just make sure you get an older, more experienced employee. I've had young guys tell me I'm wrong about stuff I've worked on for decades.

 

Thanks for your help. It is R12 and I believe the pressure is good simply by checking the low pressure switch for continuity. That may not be correct by it seemed logical. I know too it could be several things. I wad just homing in on the relay and saw the low voltage. I couldn't find any reference as to the correct voltage. I thought about jumping the compressor clutch from the battery to see if it engages but I want to make sure that 12 volts is what it can handle.
Thanks again for your help.

 

Let's not over think this. Unplug the connector on the safety switch on the receiver/dryer. Jump it with a short piece of wire. If the compressor engages, you may just have a bad safety switch. It's quick and cheap to check.

 

Compressor clutch wants 12 volts. If you are only seeing 5, I would swap out the relay, and see what happens.

 

Thanks guys for the input. I will give both ideas a try and see what happens. I'll let you all know the outcome.

 

Lots of progress this morning. I jumped the low pressure switch but that made no difference. I looked at the other relays in the engine compartment but there wasn't one that was interchangeable. So after studying the electrical diagrams in my Chiltons and double checking everything with my multitester, I hot wired the compressor clutch from the battery and came to life.
So the problem is the low voltage (only 5 to 6) going to the relay from the battery/alternator thru a fusible link (which btw is located behind the brake booster I think).
So next I ran a 12 gauge wire from the battery to the plug in for the clutch relay and it all started to work and make cold air.
Next question. How do I replace a fusible link that I can't seem to get to? Or can I just run a new one and splice it at the plug bypassing the old one altogether?
Again, thanks for all your inputs!

 

The fusible link is spliced into the wire in question, to replace it, you just splice in the new one... Think I would be more tempted to put in a fuse block, and you can install an easily replaceable fuse instead. Getting to the wires is the fun part.

 

That's my thinking too. I'll just install a permanent wire with an inline fuse direct from the battery to the relay plug. It's only about 2' and saves a lot of time trying to get at the old wiring. Thanks again!