Hi all,
I am experiencing electrical lingo overload. I've read the related links and I am now thoroughly confussed. My Aux. fans are not coming on when "I think the should". With the car running and AC on full blast the "low speed" does not come on. I can see some foam through the "spy" glass on the receiver/dryer. I have been converted to r134 and did a recharge yesterday, I still see some foam (not sure if that means I have not filled it up enough?). As things stand now, I have cold AC. I jumped the two flat connectors coming off of the presure switch and the fans come on at low speed. Second (I forgot to write first above earlier), independent of the AC, as the car heats up, the high speed fans don't come on, the only way I have to measure temp is dash guage. I jump the temperature switch and the high speed fans come on.

I am trying to figure out what to do next. Is it safe to say that if the temperature switch is good (I replace it) then that should fix the high temp fan going on issue. And if I have the AC charged to the correct preasure (volume of refrigerant) and install a new preasure switch, I should be good on that one.

I guess what I am trying to figure out is, how do I test the two switches (presure and temperature) to see if they need to be replaced prior to doing anything else (spending any more money). I understand that in order for the preasure switch to work I need to correct charge in AC system.

I have an OHM meeter, never used it before though. Can I use that to test the switches?

Thanks a lot guys, without this forum I would never have gotten this far.

Joel

I'm not sure you have a problem. Sounds like the fans and related relays are fine since jumping the two switches makes the fans come on appropriately.

Fans should come on low speed only when the pressure in the AC system exceeds a certain value. On my car, this only happens in hot weather, in stop and go traffic. In other words, unlike in some other cars, the fans do NOT automatically come on whenever the compressor is engaged.

You say the fans do not come on at high speed either. They should only come on when the coolant temp exceeds a certain value. In my car, they seem to kick in when the coolant temp shows about 100 degrees or a little more.

Unless I'm missing something, the fan behavior you've described sounds like it could be normal.

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Steve
'93 400E

Thanks Steve,
I probably did not state my note clearly enough. Trouble is, fans only come on with jump, they don't come on themselves, car get really hot and still no fans.

Joel

Hoping a couple more people read this one, I am trying to figure out how I test the preasure switch and the temperature switch which activate my aux. fans.

Thanks,
Joel

Here's a link to a thread on testing the CTS (coolant temp. switch) (sorry, don't know how to do shorter URLs):

http://www.peachparts.com/shopforum/showthread.php?threadid=16757&highlight=testing+cts


I did a search on "testing pressure switch" and got some useful info from Arthur Dalton as well but did not see a reference to
specific pressure/resistance value. The collected wisdom was that low refrigerant charge was much more likely than a bad switch, and the first order of business seems to be to make sure the AC system is adequately charged before condemning the switch.

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Steve
'93 400E

Thanks for the reply, and thanks for taking the time to do the search, I should've been the one doing that. I totally agree with you, I will bring back to the same guy who did the conversion last year (this is my first time using the converted system) and have him re-presurize the 134. Based on the looks of things, I hope that will take care of the low speed fans, I think I'll replace the tempterature switch, just to be safe on the high speed side of things.

Thanks again,
Joel

Good luck, and please keep us posted.

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Steve
'93 400E