Temperature sender differences

[skippy124]

I'll try and keep this post short....

Put in a second hand A20A4 about 6 weeks ago.... everything fine except when idling in traffic in gear (auto) after a few mins temp gauge goes up to 3/4 + before fan switches on.. then gauge goes down... fan goes off... gauge rises etc etc. Never had this problem with original motor.


First thing I tried (after reading any relevant post I could find in here)... reverse flush engine (water and compressed air...) and radiator and put in new thermostat... got a lot of junk flushed out but didnt make any difference to gauge/fan behaviour.

Second... pulled radiator and sent for full clean... (pull apart, core clean and reassemble).

Whilst waiting for a call from radiator shop to come a pick up radiator thought I would kill some time and check the temp sender in the thermostat housing. Did the pot of water on the oven and thermometer trick, and it came pretty close to figures given in manual. Thought I'd also test the sender in the old motor that was pulled, and guess what...... it was a fair bit different than the first one I tested. It gave higher resistance reading for a given temp.

Went and picked up radiator and the guy said that it wasnt blocked much and had pretty good flow before he cleaned it, and that it woundn't have been the cause of my problems.

Put radiator back in, and installed temp sender from original motor. Ran car... and bingo... no more problem.. temp gauge stays below 1/2 way now all the time.

The original motor was a 1989 A20A4, whereas the replacement motor is a 1986 A20A4... I wonder if there was a change to both the sender specs and the temp gauge later in the model run?????

I have the temp vs resistance readings I measured for both senders if anyone is interested.

Apologies for the lenghty post... had to get it out... spent two days and $100 fixing a prob that could have been fixed in 10 mins at no cost... wanted to let others know what I found.

John

[accordlxi2.0]

well i know that in the us the efi engine's were different the 86-87 compared to the 88-89.
your engine is a sohc 2.0 right??

[skippy124]

Yes, thats right SOC 2 litre. The '86 and '89 engines look identical here, same sensors, vacuum lines/controls etc.

[accordlxi2.0]

yea i just realized that, lol.
umm well it' seem's that the replacement motor temp sender was about to go out.
glad you found the problem.