recently, my temp gauge has been going up until it reaches about 1/4 of its movement, and then drops back down to below zero slowly. i know for a fact my oil pressure sender cable is faulty (no insulation) because bumps when accelerating make it flicker on and off. could the same thing be causing intermittent operation of my temp gauge? i never suspected it of running hot until just now. i let the engine idle for about 10 minutes to warm it up (reving occassionally) in order to suck a little water into the intake to start my steam clean process that we talked about in my last thread. after i was done (just water) and turned off the engine, it started smoking towards the back of the exhaust side. not a huge plume of smoke or anything, just an ethereal ghost of smoke. poetic yes, but scary. so here i am with a potentially overheating engine, no working temp gauge, and my bentley manual is across town! of course i some how managed to bring my hayes and chilton manual... quel nightmare! can anyone outline a quick test of the temp gauge and sender so i can see potentially get the old gauge working reliably for my ride to my bentley? i realize its probably the stupid wire harness which is almost non functional anyway, but how can i test it and maybe rig it for now? the coolant level is on the money, radiator is very warm to touch... can i test to make sure its circulating? could it have been that i ran the engine for a long time and didnt actually move? if the smoke was coming totally from the exhaust manifold and downpipe (which im not totally sure of) could it be ok because under normal conditions airflow cools that some?

helplessly
handsome greg

I think if it actually was overheating, you'd see some serious expanding happening in the expansion tank.

Meanwhile, you can take the yellow wire where it connects to the gauge sender by spade lug and ground it. That should send the gauge sky high. Later when you get back to where you have "stuff" again, you could substitute for the sender with a 68 ohm resistor which should give your gauge a 3/4 reading more or less.

I forgot, what year 200 do you have? Is it 86 or later with a temp compensator?

If so, whack the dash above the cluster if you haven't already.
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Art Benstein near Baltimore

MY temp gauge does the same thing. Works some times but other times hangs out at 1/4 hot or just sits below cold. Wack the dash on top of the instrument cluster and The gauge will probably work for at least a short amout of time so you can see if you are overheating or not.

There is a way to fix this and I think if you do a search on the archives you will be able to find the method. I once found it but I just have not found it that important to mess with. IF ever I am in question of heat, I just hit the dash to make sure I am ok!

Yes, it is very common with 86 and up cars to have bad connections-- a bit of corrosion-- on the temperature compensator board located in the speedo cluster.

Another source of trouble is loose gauge nuts, but the 1/4 reading sounds like the board problem. Randy Starkie has a nice write-up on eliminating the board and the problem. Here's how I do it:

Here's the temp comp board.

so wait i complete remove the board forever and just jumper those terminals?

The theory I hear most is Volvo put that board in beginning 1986 to smooth out the little dance the needle does in response to a normal overshoot of gauge temperature as the thermostat opens. I guess it was a response to the cost of warranty complaints caused by the gauge action.

Removing the board and adding the jumper makes an 86+ respond like up to 85. Ipd sells a kit that just plugs on the terminals, so I'm sure you can read more about the reason for this at ipdusa.com but in the end it is up to you. They also sell replacement boards, but you'll see in the Bentley a paragraph, I think, describing the cleaning of those contact pins as another way to fix it. All depends on whether or not yours behaves after a dash whack.
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Art Benstein near Baltimore

yeah i get it now. i'll be jumpering that tomorrow morning. it'll be nice to get a reading on the thing, and honestly i'd prefer the non buffered reading. the ipd kit instructions did work out. i can't believe they charge $15 for a jumper wire. then again, i wouldnt accept less than $20 each to start manufacturing them and dealing with customers... god i hate customers. anyway, thanks for the info! its quite a relief!

handsome greg

temp faker.... im at a loss for words.

handsome greg